Taste the Rainbow…Cake!

Photo 09-06-2013 15 39 36It’s a rare occasion for me, to have the chance to make someone a birthday cake. Usually, there’s a fair amount of pressure, whereby it has to be perfect. It has to look good, you can’t just say ‘ah that’s alright, it’ll do’. Aside from the fact it is FOR someone, to a certain extent, there is an element of showing just what you can do. For me, I wasn’t too great at baking this time last year, so as time has gone on, I have tried to teach myself things and improve. At one stage, I considered trying to gather the funds together to try and do a year at a cookery school/college. I had to face facts, there would be no way I could afford to go to schools such as Leiths or Le Cordon Bleu around the age I am now, INCLUDING being in debt to the Student Loan Company…

What I did realise though, is you can learn all of these things off your own back; Youtube videos, cookery and baking books, recipes online, and of course WONDERFUL BLOGS! When I first bought Edd Kimber’s ‘Say It With Cake’, I remember flicking through it and thinking ‘oh gosh, there’s no way I can do that’. As the months have gone on, I came back to it and decided to give it a go…the rainbow cake.

I see a lot of hype about rainbow cakes everywhere, and most of the recipes are vastly different; different layer thickness, number of layers, type of icing, measurements and so on. I can understand why these cakes are so exciting, and for the person who has made it, a degree of smugness washes over you when it’s cut into. Seeing all those layers perfectly sized and sandwiched together…you can’t beat it. The way to describe this cake is, unicorn sick. IT’S SO BRIGHT AND COLOURFUL! Photo 09-06-2013 15 37 58

Edd Kimber’s version is an absolute monster, it’s huge and it’s proud of the fact; it uses 6 individually coloured and baked layers, and is timing consuming. It also uses a horrifying amount of butter in both the cake and especially the icing, but it is designed to be eaten by a lot of people (approx. 18). The icing itself uses the Italian meringue buttercream method, which takes forever if you’re using a hand mixer and not a lovely standalone one (I’m jealous of those who do!). My last word on it is, if you’re in a rush don’t even bother. I made all the sponges the night before, and then made the frosting the next morning; but the time spent on it is well worth it by the look on the person’s face when they see it. A special thanks to Stephanie @ Riverside Baking for lending me the colours, check out her blog too!


For the sponge layers:

  • 225 g unsalted butter (+ extra for greasing)
  • 325 g plain flour
  • 50 g cornflour
  • 4.5 tsp baking powder
  • 1/2 tsp salt
  • 400 g caster sugar
  • 2 tsp vanilla extract
  • 4 eggs, separated – you need both the yolk and white
  • 300 ml whole or semi-skimmed milk
  • Gel food colouring in redyelloworangepurple, blue and green

 For the white chocolate Italian meringue frosting:

  • 150 g white chocolate
  • 300 g caster sugar
  • 6 medium egg whites
  • 540 g unsalted butter, at room temp


  1. Preheat the oven to 180C/fan 160c/gas mark 4. Grease and line the bottoms of 3 x 20 cm/8″ round cake tins, or bake one at a time if you don’t have 3, also greasing the baking parchment. Whisk the flour, cornflour, baking powder and salt together in a bowl and set aside.
  2. Add the butter to a clean large bowl and beat with an electric mixer until smooth and light. Add the sugar and continue to beat until it becomes light and now fluffy! Add the vanilla and mix to combine; while the mixer is on a medium speed, add the egg yolks one at a time and beat until incorporated. Change the speed to low, sift in the flour mixture in 3 additions, alternating with the milk (starting and finishing with the flour).
  3. Add the egg whites to a grease-free bowl and whisk until the hold soft peaks. Add the whites to the cake batter and fold gently until just combined with no streaks of white. Photo 08-06-2013 20 59 59
  4. Divide the batter equally between 6 small bowls; add a small amount of each colouring to each bowl, you need enough to make it vibrant. Add the first three bowls to the prepared tins (or however many you have) and bake for 15-20 mins, they should spring back when lightly touched. Allow to cool in the tin(s) for 10 minutes before turning out on a wire rack to finish cooling completely. Repeat with the rest of the batter.Photo 08-06-2013 23 04 10
  5. Now we need to start making the frosting; melt the white chocolate in a heatproof bowl set above a pan of simmering water (or in the microwave for 30 second bursts). Remove from the heat and allow to cool.
  6. Add 190 ml of water and the sugar into a pan on a medium heat. Bring to the boil and get your sugar thermometer ready! While the mixture increases in temperature, put the egg whites into a bowl; begin to whisk these on a high speed when the syrup reaches 115C on the thermometer. Cook until it registers 121C. With the mixer still on, pour the syrup in a slow stream down the side of the bowl, avoiding the beaters.
  7. Continue to whisk on a high-speed until the temp drops to approximately 20-24C, I found this took a long time using an electric whisk, but is probably best done with a freestanding mixer.
  8. Once the temperature reaches 20/24C and with the mixer on a medium-high speed, add the butter a few pieces at a time, beating until combined. This can look curdled, but keep mixing (patience is a virtue). Eventually it will smooth out to form a light buttercream; pour in the melted chocolate and mix until combined. Photo 27-06-2013 23 57 31
  9. To assemble, put the purple layer on a serving plate and top with a thin layer of buttercream. Repeat the process with the other layers in the following order: purple, blue, green, yellow, orange and red; spread the remaining frosting across the top and sides of the cake. Decorate with colour sprinkles or stars as desired. Photo 09-06-2013 13 59 08


4 thoughts on “Taste the Rainbow…Cake!

  1. riversidebaking says:

    AMAZING! Big Mwah for the mention! I love this cake, can you make it for cake club one day! I’ve had mixed results from the Edd Kimber book, cookies great, macarons failed – but maybe it was me 😉

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