How to make a Rainbow Layer Cake using white chocolate mud recipe

Rainbow Cake
Rainbow Layer Cake

This cake is similar to my Rainbow Cake below and you can find full instructions for it here.

Rainbow Cake
Rainbow Cake

Three things make this cake special

1. The Rainbow Layers. They can be a big surprise if the recipient and/or guests have no idea what is inside.

2. The cake is based on a White Chocolate Mud Cake. Lots of people are scarred to use colours with Chocolate mud cakes if they do not have the special chocolate colours. I did a lot of research before I used my ordinary food colours and the reason they work is because we are not colouring 100% pure chocolate. The other ingredients magically make it alright to use Wilton or AmeriColor (these are the only two makes that I have tried so far).

3. You can make this cake even if you do not have 6 x 10″ round cake pans. I have 2 x 10 inch pans and I bake the layers in 3 batches. You could make do with just one pan, it will just take a little longer.

Colours of the rainbow
Colours of the rainbow Red, Orange, yellow, green, blue and purple.
Coloured cake batter
Coloured cake batter
Use 2 x 10 inch pans
Use 2 x 10 inch pans

White Chocolate Mud Cake 

(Planet Cake recipe)

Need a minimum of one 10″ pan ( 6 x 10″ pans would make the job really easy though!)

I used 2 x 10″ pans as that is all I have.

390g butter
390g white chocolate
350ml water
195g SR flour
390g plain flour
520g caster sugar
4 eggs, lightly beaten
2 tsp vanilla essence

White Chocolate Mud Cake Method

  1. Preheat the oven to 150C.
  2. Grease and line bases of both cake pans with one thickness of baking paper.
  3. Combine chopped butter and water in a saucepan.
  4. Stir over low heat until butter is melted. Turn off heat, then add the chocolate and stir until it has melted and is well combined.
  5. Sift flours into a bowl. Add sugar, a pinch of salt and make a well in the centre.
  6. Pour chocolate mixture, egg and vanilla into the well then stir with a wooden spoon until well combined.
  7. Divide the batter equally amongst the 6 bowls.  Weigh your mixing bowl before you begin adding ingredients and then subtract the weight of the bowl from the final measurement after the batter is completed. Divide that number by six and add that weight of batter to each bowl, and then whisk a fair amount of the appropriate food color into each bowl. Keep in mind that the color of the unbaked batter will be the color of the baked batter. Pour into the pans and bake for 15 minutes each or until a skewer comes out clean when poked into the middle of the cake.
  8. Once cake pans have been washed, repeat the process twice more till all 6 layers have been baked.


Rainbow layers ready for buttercream
Rainbow layers ready for buttercream

Lemony Swiss Meringue Buttercream

As you can see from the recipe, this cake requires a huge amount of buttercream to fill the layers and cover the outside. I would recommend that you make the buttercream in two separate batches ( 1. To fill and crumb coat. 2. To frost) because you would need a HUGE bowl to make this much buttercream at one time!

Please click here for a step-by-step guide to making Swiss Meringue Buttercream and troubleshooting tips!

To fill and crumb coat:

9 egg whites
1 ¾ cup (350 g) sugar
4 sticks (452 g) butter, room temp
2 tsp lemon extract

To frost:

5 egg whites
1 cup (200 g) sugar
2 sticks (226 g) butter, room temp
1 tsp lemon extract

Cook the egg whites and sugar in a small saucepan over medium heat, whisking constantly, until the sugar is completely dissolved (test by rubbing some between your fingers. If it’s completely smooth, it’s done). Pour into another bowl (a stand mixer is preferable) and whip on high speed until room temp. Then, on a medium-slow speed, add the butter, waiting until each piece is completely incorporated before adding the next. After all the butter has been added, turn the mixer back to high speed and whip until it has come together, about five minutes. Add the extract, beat briefly and then use.

If the buttercream seems soupy after all of the butter is added and does not come together after whipping, refrigerate for 5 to 7 minutes and continue whipping until it becomes fluffy and workable.

Filled with buttercrem
Filled with buttercrem


Stack the layers in your preferred order and fill and frost as you would any other cake.

Once frosted, the cake can be left on the counter without any problems, but feel free to refrigerate it. Just be sure that the cake is at room temperature when serving or the frosting will be hard.

A slice of Rainbow Cake
A slice of Rainbow Cake

22 thoughts on “How to make a Rainbow Layer Cake using white chocolate mud recipe

  1. This is hands down, the BEST rainbow cake recipe ever! The layers worked out perfectly, the cake was moist and your instructions are very easy to follow. It’s so nice to see a chocolate mud recipe instead of the standard vanilla cake! I made a ‘practice’ cake to see if it would work out nice enough to make for my daughter’s 3rd birthday next month and it was absolutely divine! For her BD cake I’ll pipe the icing in rows of coloured flowers to match the inside of the cake. Thankyou so much for sharing!

  2. I have just made your rainbow cake for my granddaughters 5th birthday and it was excellent. I made it into a princess castle cake (her words) and she wanted ninja turtles on it and a model of her and her brother. It was a 2 tier cake ( it had to be to fit all the stuff she wanted on it) Thank you for the great recipe and I will be using this again.

  3. Hi, I will be trying this cake for my son’s 4th birthday this weekend – this will be a bottom tier of his 2 tier cake. Can you tell me how tall was your cake? Thanks in advance.

      1. Hi again, Bernice,
        This cake needs to be made ahead of time and will be served at a 2yr olds birthday party in the park on Sept. 27th. How early can I safely make it and how do I store it? Also, would it be ok standing outside if the weather is warm. Oh, my, such a dilemma for the Grandmother! Cheers, Helene

      2. You can bake the cake say 5 days ahead as long as you cover it with 2 layers of cling film when cool. Store in fridge till you are ready to cover in buttercream. Always bring cake back to room temperature before covering with buttercream.You can store your finished cake in the fridge till the party. All will be well outside unless temperatures go up to 27C. If they do then put in a large cool box with ice blocks to keep cool. Do not put the cake in direct sunlight whatever the temperature.

  4. I haven been looking for a white chocolate mud rainbow cake and can’t wait to try it, will be making it for my daughters birthday tomorrow. With the buttercream, is it easy to get smooth and the. Imprint as I am making a castle and need to have the brick look?

  5. Hello there! Please could you tell me how many servings you got out of this? I want to make this but need it to be big enough for 25 adults. Many thanks!

  6. Hi Bernice, thanks for your instructions & also huge thanks for including the gram measurements (being a fellow Aussie I don’t get the sticks thing!) but just wondering if you use buttercream between as a personal preference? Does it work better than ganache?

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