How to make the most delicious cake filling

Β I made this filling for Ava’s birthday cake and let’s just say, she was lucky I didn’t sneak into the kitchen in the middle of the night to lick it all out of the centre, it was that delicious.

The filling is a variation on Warren Brown’s Italian Meringue Buttercream (IMBC) which I have mixed with a sticky date pudding sauce to make a caramel meringue filling for Ava’s caramel mud cake……yum yum YUM!

Before we get stuck in to making our IMBC, we need to make our caramel sauce so that it has enough time to cool down and thicken.

Bring to the boil:

150g Brown sugar
150ml Cream
50g Butter

And then simmer 5 minutes before setting aside to cool down and thicken up

Next it is best to measure out our ingredients for the IMBC.

5 egg whites from extra-large eggs

455g of unsalted butter, cut into small pieces and set aside so that it can come to room temperature

285g castor sugar, plus 55g in another bowl

1/4 cup water

When making Italian Meringue Buttercream (IMBC) you need to make sure your bowl is completely clean from the last use. Egg whites wont whip properly if there is remaining fat in the bowl, so I like to clean my bowl and whisk attachment with some alcohol.

So… grab your trusty bottle of vodka from your handbag πŸ™‚Β and a paper towel and give everything a good clean.

Next up, separate your eggs and start your mixer on a slower speed… gradually working up to the highest speed as the egg whites start to bubble.

At this point, you can put your 285g sugar and water into a pan over a high temperature with your sugar thermometer (you can use the thermometer to stir the sugar until it has dissolved).

I know you are thinking ‘what the heck is a sugar thermometer?’ and yep, I was thinking the same thing when I first read the recipe. You can pick one up off ebay for about $10 and it is really important to have one to gauge when your sugar syrup is at the right temperature (if you leave it that bit too long, it will turn into caramel).

While your syrup is boiling away, your egg whites should be nice and fluffy, so keep the mixer on and add in the remaining 55g sugar

Keep the mixer on and go back to your stove to check on your syrup. It needs to boil until the temperature reaches 249F.

Your mixer should still be running (in fact, from the moment you turn your mixer in, it should remain on until you have finished the whole recipe), so carefully pour the boiling sugar syrup into the mixing bowl

Ideally it would have been great to have shown you aΒ  pic of me pouring the sugar syrup into the mixing bowl, but the combination of a heavy SLR camera, boiling hot sugar syrup and 3 children watching me was not ideal!

If you put your hands around the mixing bowl, you’ll notice that it is quite hot. The mixer needs to keep beating until the mixing bowl is at room temperature (or thereabouts). It generally takes about 10mins and in this time the sugar syrup is cooking the meringue (yum yum).

Once the bowl is at room temperature, grab your butter and one by one, drop it in the bowl (if your mixing bowl is smaller than mine, you may want to place a tea towel over the top of it so that bits of butter and meringue don’t fly around the room.

Keep mixing for a few minutes until it is all combined

I made this batch of IMBC to fill two cakes, so it does make a decent amount, but any leftover can be stored in the fridge in an airtight container for a few weeks.

I mixed about 1/3 of the IMBC into my caramel sauce

And that is it!! Seriously the most delicious filling I have ever tasted. It could easily be used to ice cupcakes and I think I will try and make some caramel cupcakes with this icing to test it out.

I used this filling for my 6″ mudcake which I levelled using my cake levellerΒ because I don’t trust myself to cut straight myself! This is really easy to use as you adjust the notches on the size for the preferred height and then you saw away and end up with an even cut.

I generally bake my mud cakes in advance and then freeze as I find they are much more moist this way (and it helps save time). I also prefer to level and tort my cakes before they have fully defrosted.

Once you have made your layers, it is simple to just cover each layer and set aside ready to ganache and ice.

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54 Responses to How to make the most delicious cake filling

  1. Juliana October 24, 2012 at 11:57 pm #

    My name is Juliana, I’m from Brazil!
    I’ve been living in the USA for 2 years!
    I cook cakes and I realy want a very good filling to put in my cakes! Because brazilian fillings are differents than american fillings! When I found your web site I started to do a lot of things that you teach here! I’ts very good! I’m enjoying a lot!
    I have a question about the most delicious filling! What kind of cream do I need to put with a brow sugar? And the eggs are only the white part? When I need to put the yellow egg part?
    Thank you SO much for do this site! It’s very useful!

    • BronnieBakes Admin November 1, 2012 at 7:51 am #

      Hi Juliana and thankyou for your lovely comments πŸ™‚

      I just use standard cream – I think it’s double cream… but any cream should work (not the prewhipped cream though). The runny cream!

      And yes, it is just the white part of the eggs. You can save the yellow part for making some custard, or I generally through them away.


  2. December 5, 2012 at 1:33 pm #

    I just love your site!! I want to make this but I only have a Kenwood mixer with a plastic bowl. DO you htink it would work the same if I made it with a stainless steel bowl and a hand mixer?

    Cheers, Sarah

    • BronnieBakes Admin December 5, 2012 at 1:44 pm #

      Hi Sarah

      thankyou πŸ™‚

      Yes, it would work if you used a hand mixer, but it would be a bit of a pain having to stand there for so long!!! You could always use your kenwood mixer and just let it mix for 15 minutes and then add the butter. You can always stop the mixer and feel the mixture to see what the temperature is like

      Hope that helps!

  3. December 5, 2012 at 2:23 pm #

    I just wonder how well the egg whites would whip in the plastic, what do you think?

    • BronnieBakes Admin December 5, 2012 at 2:38 pm #

      I ‘think’ the problem with using a plastic bowl is that there may be traces of fat… so you could try it and just wipe the bowl well with alcohol.

      I think I’d rather try that rather than stand with a hand mixer for 10-15 minutes!!!

      All the best and let me know how you go!


      • tsoldaker December 5, 2012 at 3:06 pm #

        ha ha ha, thanks I will do!!

  4. tsoldaker December 6, 2012 at 2:04 pm #

    Just wanted to let you know that I have just successfully made my first Italian Meringue Buttercream πŸ™‚
    I just wish I could attach a photo of it for you!!
    It worked in the plastic bowl just fine, and actually I think it cooled quicker than ifit had been in metal. I did find though that my sugar syrup had turned golden before it had hit 249.F – it’s ok though, it’s just not as white. I have a brand new therometer so I’m not sure what happened there…

    Also, the cream seems quite soft, does it stiffen up more upon standing?

  5. tsoldaker December 6, 2012 at 2:44 pm #

    Thank you!!!!!

  6. Michele December 9, 2012 at 3:58 am #

    Is “Castor Sugar” the same as powdered sugar?


    • BronnieBakes Admin December 9, 2012 at 12:23 pm #

      HI Michele

      I think powdered sugar is what we call icing sugar. Castor sugar still has granules like normal white sugar, but they are smaller. They have been ground down a little more (but not so much that it has turned into powder)

      Hope that helps!

  7. Gloria February 23, 2013 at 7:35 pm #

    Hi you have a very fun site. I have watched some of ur tutorials.. I want to try your IMBC with caramel, thank u for sharing! From ur new fan from the Philippines!

    • BronnieBakes Admin February 24, 2013 at 9:48 am #

      Thanks for stopping by Gloria!! Yes – definitely try the caramel IMBC – it is SO yummy!!


      • Gloria March 30, 2013 at 12:48 pm #

        Thank you !

  8. Maria April 2, 2013 at 1:09 pm #

    This looks fantastic!! 2 questions can I use this icing in a cake that I will cover in fondant?
    Can i add any flavour to it? like melted chocolate?
    thank you!!! Love your web site!!
    Maria x

    • BronnieBakes Admin April 2, 2013 at 3:53 pm #

      Yes – absolutely! I use it as filling for most of my cakes and I add lemon curd to make a yummy lemon meringue filling and definitely chocolate is delicious!


  9. Irene May 20, 2013 at 7:32 pm #

    I found your website when I was doing research for my son’s first birthday party. We are having a very hungry caterpillar party. We have already made the decoration of the cake – my husband had so much fun making the caterpillar.

    So now all that is left to do is to make a cake. I am from Austria and simple buttercream is so outdated here – that is something people used have to have in the 70s. For my daughters birthday I made Swiss Merengue Buttercream and I fell in love with the texture. I was delighted when I found out that you could flavor your buttercream. But that leaves me with some questions:
    – Does the flavor affect the consistency of the buttercream?
    – Why do you only flavor the filling of the cake? Does the added chocolate/lemon curd affect the fondant?

    Thanks for your help. I love your website and I am already following you on pinterest and facebook πŸ™‚

    • BronnieBakes Admin May 20, 2013 at 8:59 pm #

      Hi Irene

      Thankyou for your lovely message! I am so glad to hear you have made the hungry caterpillar cake. To answer your questions..

      I use thicker flavours to flavour my filling. For example, using lemon curd which is quite thick, or a caramel sauce, or chocolate ganache. If you use a runny flavour then yes, it will affect the consistency of your filling. I often have more trouble during hotter months as it affects my italian buttercream anyway and I usually need to let it rest in the fridge for a while.

      i don’t quite understand your second question though? I add flavouring to my filling but my cake is usually flavoured… so if I add caramel filling, my cake is usually a caramel mud cake, and likewise with a lemon curd filling, my cake is a lemon mud cake, dark chocolate/white chocolate etc…

      Does that helps?? thankyou for following!!


      • BronnieBakes Admin May 20, 2013 at 8:59 pm #

        *help.. not helps!

        • Irene May 20, 2013 at 9:22 pm #

          Thank you for your help πŸ™‚

          My question was whether you put the flavored buttercream only in the middle, or if you also use the flavored buttercream also right under the fondant (on the outside of the cake). If I put lemon curd in the buttercream that goes right on top of the cake – would that added lemon curd melt the fondant?

          I am planning to make a yoghurt-strawberry filling or a curd-mandarine filling for the cake. But the filling would be too wet, so I need something do isolate it from the fondant. Therefore I need the buttercream on the outside of the cake. But ordinary buttercream won’t match the yoghurt filling – which is a little bit sour in taste. That’s why I need to flavor the buttercream – but I am afraid if I put something wet (like lemoncurd) right under the fondant that it will melt the fondant.

          • BronnieBakes Admin May 20, 2013 at 9:33 pm #

            Aha… now I understand. I don’t use buttercream on the outside of my cake. I use it for the filling and then I use chocolate ganache for the outside as it gives a yummy flavour, seals the cake and also makes a great smooth shell for applying the fondant.

            Most decorators in Australia use ganache under fondant… most Americans use buttercream. I definitely prefer using ganache! A white chocolate ganache would work with your yoghurt filling. I have my method here if that helps?

            Use a 1:2 ratio of cream:white chocolate

            hope that helps!

  10. Alice May 31, 2013 at 6:06 pm #

    Hi, thank you so much for sharing all of these fantastic tips and tutorials. Even my four year old requests to watch you making the lego men/lego cake!!

    I am wondering if the IMBC is okay in place of buttercream as the outside layer for a cake that is not being iced with fondant? Is it hard enough? or would I need to refrigerate the cake once iced or just treat the same as if I used standard butter cream? Also, I would plan to colour the IMBC which shouldn’t affect the consistency too much?

    Thank you!

    • BronnieBakes Admin June 1, 2013 at 8:27 pm #

      oh that is so sweet Alice!! πŸ™‚ thankyou

      yes, absolutely! It will harden like buttercream as there is a fair amount of butter in the recipe. If I am not covering my cake with fondant then i just use IMBC around the cake. It depends on your climate as to how hard it will go, but if it isn’t hard enough then the fridge will certainly harden it. You can easily refrigerate it, but you don’t have to because the egg is cooked.

      Colouring shouldn’t affect it at all – you do need to use gel colouring and not that liquid colouring from the supermarket. That said, even liquid colouring shouldn’t alter the consistency too much as if I’m flavouring IMBC i add a fair bit of liquid and it is fine.

      hope that helps!


  11. Debby August 5, 2013 at 9:44 am #

    Thank you for sharing this! I made this yesterday, it was delicious! The caramel filling was so, so good and the regular Italian Meringue Buttercream worked perfectly for piping decorations on cupcakes. I ran out of eggs and had to mix up some regular Buttercream, and lets just say it doesn’t taste nearly as good as I used to think. I am ruined and may never make regular buttercream again, I’m so glad I found your site.

    • BronnieBakes Admin August 5, 2013 at 3:57 pm #

      that is great to hear Debby! I absolutely ADORE the caramel IMBC and I’m so happy to hear you had great success with it. Thanks for letting me know!


  12. Nis August 8, 2013 at 4:27 pm #

    I live in Sri Lanka and My mom runs her cake class and she does cake for orders, but this time for our Eid festival i want to surprise my mom with something new which she has not tried! and i think your IMBC will be the best choice, but i have some questions to ask, since im doing this secretly, I did not get to buy any cream therefore i would like to know if i could use anything else other than the caramel, may be like chocolate fudge?
    If so, can i know what would go well with this icing?

    Thank you….

    • BronnieBakes Admin August 9, 2013 at 8:34 am #

      Yes – absolutely! I use some melted chocolate when I want a chocolate flavour, or lemon curd is amazing for a lemon flavour and fresh berries is great as well

  13. Nis August 8, 2013 at 4:30 pm #

    Hi again…..
    Or can i omit the cream for the caramel and add something else instead?

  14. Carly August 9, 2013 at 2:56 pm #

    Hi Bronnie,

    Stumbled across your page and fell in love!!

    I need your help!

    I have attempted to make IMBC on a few occasions now (using this recipe) and it doesn’t seem to be “fluffy” looking at all after all the butter is Incorporated. It almost looks like a curdled cake batter!! :/ not sure what or where I’ve gone wrong!!

    • BronnieBakes Admin August 11, 2013 at 11:13 am #

      Hi Carly

      Thanks for your lovely comment!

      That is a shame to hear that, but it is easily fixed! Your batter will curdle if your sugar mixture and butter are not the same temperature. So.. you need to have your sugar/eggwhite mixture beating away until it is room temperature. Then you need to make sure that your butter is around room temperature as well. I actually put my butter in the microwave for a few seconds to soften it (esp now that it is winter!) and when you add the butter it should be hard to lift in one piece from the plate because it is soft. If you find that your mixture is curdling and not coming together you keep your machine running and get a dishcloth, run it under boiling hot water, squeeze the excess out and wrap it around your mixing bowl (so you are warming up the bowl). After 5-8 seconds the dishcloth will be cold again, so keep doing this 5-10 times and your mixture will come together in the end.

      Does that make sense? hope that helps πŸ™‚


  15. Trace October 21, 2013 at 10:16 am #

    Very happy that I came across your site πŸ™‚
    I have done many cakes but not normally caramel mudcake & I have never used butter cream only ganache as filling also.
    I am needing to make a 12″ x 3″ in caramel mud cake. So I am going to give your recipe a go, how many quantities do you suggest ?
    I personally dont like butter cream but your italian caramel butter cream sounds beautiful. Just a few questions though, how long does it keep for & how far in advance can you fill the cake & then ganache seal & also is this suitable for cakes that will not be refrigerated ?
    Thanks in advance πŸ™‚

    • BronnieBakes Admin October 21, 2013 at 10:26 pm #

      Hi Trace πŸ™‚

      Thanks for your message! I am not the best judge for quantities, but I would say more than one batch only just! Just to be safe, make 1.5 times and if you have a higher than normal cake, then so be it. Or, any leftovers can be made into mini cakes or cupcakes.

      The caramel IMBC is simply AMAZING!!!! It will keep for 3 weeks in an airtight container or up to 2 mths in the freezer, but personally I like to make it and use it straight away. I usually fill and ganache my cakes two days before the event and then cover with fondant and decorate the day before the event. Once you ganache your cake you are effectively making an air tight container for the filling so it will be fine. That said – if it is ridiculously hot where you are, I would keep the cake in a cold room (or in front of the air conditioner if you have to).

      Hope that helps!

  16. Caroline January 27, 2014 at 5:54 pm #

    Hi Bronnie,
    I’m writing again with another question because I love everything I have seen you make and I feel like i can trust you on ingredients :).
    I think I have read almost every post on your site (not EVERY, but getting there!), and I love your recipes and tutorials – I see you have recipes for cakes, and fillings, and of course Italian meringue buttercream – but what fondant do you use? Do you make your own? Do you use a prepared brand? And if so, which brand? I’m trying to decide if it’s worth all the work of not only baking cakes from scratch, mixing up fillings and buttercreams from scratch, cutting out and molding and assembling decorations and designs, but ALSO making the fondant too.

    • BronnieBakes Admin January 27, 2014 at 6:20 pm #

      Hi Caroline πŸ™‚

      I have never actually made my own, although I think I will give marshmallow fondant a try this year, but only as an experiment. As you say… to make a cake from scratch, icing and then to decorate it already takes a fair bit of time!! So I’m not really keen to add any extra time into the equation.

      I use Bakels fondant which I buy in bulk (7kg boxes) in white. If I need a strong colour (black, red, blue, green etc) then I buy a premixed colour in the Satin ice brand.

      Hope that helps!


      • Caroline January 28, 2014 at 12:30 pm #

        Thanks, that does help – insofar as making me feel better – if you don’t make your own, then I can do that too!
        I’ve been using Wilton’s so far and have been pretty happy with it. I read so many negative things about it online, though, and about packaged fondants in general, that I wondered what you use and if I needed to take the next step to making my own :). I’ve also been deliberating about whether to give Satin Ice a try. If it’s significantly better I would do it, but otherwise not because it’s more expensive and not as readily accessible.
        What do you think?
        Also, when you add color to white fondant do you knead it in by hand or do you mix it in your KitchenAid?
        When (if) you add color to your IMBC, do you mix that in by hand after you’ve whipped up the icing, or do you add the gel paste to the bowl and let the mixer do the work? (And would it stain your mixer? And would that matter :)?)
        Thank you so much for all your help – no one in my family does this, nor any friends, so I’ve had no one to ask for advice – I’ve just been feeling my way, guessing and experimenting, and of course, watching tutorials and reading blogs all night :).
        Hooray for you and your site!!

        • BronnieBakes Admin January 31, 2014 at 1:27 pm #

          Hi Caroline πŸ™‚

          I’ve never heard of Wilton’s fondant. But Satin Ice I have and I do like that but if Wilton’s does the trick then I would just stick with it πŸ™‚

          I add colour by hand (wearing gloves of course!) to fondant. But when adding to IMBC I just add to the mixer and I havent had any problems with staining (my bowl is steel)

          No problem at all – I’m happy to help!!!


  17. Rachel February 6, 2014 at 10:37 am #


    I have just made the IMBC and caramel to make the caramel filling and mixed it together. It tastes wonderful. Thank you for your website. I have some caramel IMBC left. How long will it last in the fridge it it’s already mixed together?


    • BronnieBakes Admin February 6, 2014 at 3:06 pm #

      HI Rachel πŸ™‚

      How delicious is it?!! I usually have to throw out my extra to stop me from eating it!! But it will keep in the fridge in an air tight container for 3 weeks and you will have to re-whip it if you wish to use it.

      Hope that helps!

  18. Diane February 10, 2014 at 8:55 pm #

    I have not tried IMBC before so on the weekend I thought I would give it ago. Your site makes it so easy. It is just the best thing. Looks silky and comments I got was unbelievable for my cupcakes. Thanks so much

    • BronnieBakes Admin February 11, 2014 at 7:57 am #

      That’s so wonderful to hear!!! I’m glad you loved it πŸ™‚

  19. jezrel March 1, 2014 at 6:18 pm #

    Stumbled upon your blog by seeing one of your cakes on pinterest. I am a new fan in England….love everything in your blog. Your cakes are amazing! I’d definitely try your recipes esp the cakes. Keep it up.

    • BronnieBakes Admin March 3, 2014 at 10:36 am #

      Thankyou so much for your lovely comment! Definitely give the recipes a try πŸ™‚


  20. Cath March 25, 2014 at 2:40 pm #

    Hi Bronnie

    I have used your IMBC recipe heaps and love it. I am making a cake for a friend that needs it to be dairy free. Have you ever tried to make it with nuttelex?

    I am giving it a go but think it might be an epic fail.



    • BronnieBakes Admin March 25, 2014 at 8:38 pm #

      HI Cath – no, I have never tried it!! An alternative could be to just make the meringue part and use that around the cake and you could torch it on the outside. All the best!

  21. Cath March 25, 2014 at 9:09 pm #

    Well it seems to have worked ok. Not sure it will hold up fondant. I added a bit of copha as well.

    I think I will forget the fondant and just use the ‘buttercream’.

    Thanks for your blog by the way. It’s great for a baking nerd like me.

    • BronnieBakes Admin March 26, 2014 at 6:58 am #

      Thanks Cath – I appreciate it!

      ps – Does the IMBC taste ok??

  22. Jan May 28, 2014 at 11:18 am #

    Hi! I’m new to baking. I love your tutorial. How do you keep your cake moist? Bake it and freeze it immediately and then cover the following day?

    Also, would you be able to send me the printable for gruffalo? I’ve been all over your site. I will try to do caramel mud this weekend.


    • BronnieBakes Admin May 28, 2014 at 1:15 pm #

      Hi Jan πŸ™‚

      I bake it, then once out of the oven I brush it with boiling hot water, cover with foil and then a tea towel and leave overnight to cool down. Then I wrap it in glad wrap and put it in the freezer. I will send through the gruffalo printables now for you

      All the best!

  23. Wirda June 27, 2014 at 9:41 am #

    Hi Bronnie,

    As you know I love this filling, just wanted to say that my filling curdled and I was totally devastated but then I thought hey Bronnie might have a solution.
    The tip of using a hot towel worked perfectly, thanks.

  24. Mandy August 29, 2014 at 7:13 pm #

    Hi Bronnie,

    I am going to soon try this filling with your caramel mud cake recipe as it sounds amazing!

    Just a question that you torted for cake into 3 layers – so you made only one batch of your caramel cake and it baked such a high cake?


    • BronnieBakes Admin August 30, 2014 at 8:25 am #

      Hi Mandy πŸ™‚

      Yes – but that cake is a 6 inch cake. It does however make a lot of icing – most of the time I never use all of it! you can always make extra and use it to ice chocolate cupcakes. Or you can freeze it.


  25. Cheryl September 26, 2014 at 5:39 am #

    Hi Bronnie I made my IMBC by following your instructions to the letter, it turned out perfectly. I had it in the fridge for a couple of days bought it out and bought it back to room temperature then added the caramel sauce I had made that day after it was at room temperature. The whole thing curdled and I had to throw it out. The party I am making this for is tomorrow so will try making it on the day, but, is the trick to add whatever flavouring just after the buttercream has come together when first made? My baby shower cake and toppers are coming along beautifully thanks to your easy instructions, thank you, just have to master this buttercream. Thanks, appreciate all your advice.

    • BronnieBakes Admin September 27, 2014 at 7:13 am #

      Hi Cheryl – yes – you do add flavourings in once you have made the IMBC. I personally make my IMBC the day I need it as I think the texture isn’t quite the same if you freeze or refrigerate it.

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