Rainbow cake for Rainbow Theme Birthday Party !

My youngest daughter turned 8 years old in October.
She is a very lively and funny girl so I decided that “the colors of the rainbow” would be the perfect theme for her birthday! So you can imagine there was no other choice than to try the famous RAINBOW CAKE  …  so here I am, checking recipes online, asking friends and colleagues for ideas, which kind of cream I will put inside the cake and for the frosting …I realize there was many options but I finally came up with the one below and I must say I was quite happy with the results ! I certainly got the “WOWs” I was expecting when I cut the cake … and also after the first bite 🙂         Mission accomplished !

 Ingredients (for a round cake of 20cm / 8 inches) :

For the 6 cakes (called “Genoise” in French):
In that case, I will actually do 6 thin cakes , that is why you will find 6 times the same ingredients, it is just the food coloring who will change:

  • 6 eggs
  • 6 X 30 g of flour
  • 6 X 30 g of granulated sugar
  • 6 X the tip of a knife with baking powder
  • Purple, Blue, Green, Yellow, orange, red food coloring
  • Salt

For the frosting/ganache: To be done in advance as it has to chill for 3hrs (or to be done the evening before :))

I actually used the same “cream” for the frosting and to fill in, in between each layer of cake. It is called in French : “Ganache Montee”

  • 300g of white chocolate
  • 300 g of full fat sour cream
  • 1 tbsp of butter


 Prepare the Ganache/frosting in advance:

  • Break the white chocolate in small cubes
  • In a pan, put the full fat cream to boil
  • Once the cream has boiled, gradually pour it on the white chocolate while you keep on mixing
  • Finally add the butter
  • Leave to chill for 3 hrs (or the entire night if you decide to do it the evening before)

 To be done 6 times (for the 6 colors) :

  • Oil and flour your cooking  pan and preheat the oven to 180 degrees C (=350 degrees F)
  • In a small bowl, mix (fast speed) together the egg yolk and the sugar until it becomes light/white color
  • In another bowl, beat the eggwhite (with salt) until stiff
  • Then, incorporate together the flour and the baking powder in the wet mix.
  •  Then add ¼ of the beaten eggwhite with a wooden spoon.
  • Gradually and gently, add the rest of the beaten eggwhite until smooth.
  • Finally, add food coloring
  • Scoop the batter in your cooking tray and bake for 5 to 7 min (check from time to time as the cake should not get dark, but keep its light color and moist)

Clean your cooking tray in between each cake. While you cook the other thin cakes, keep your other cooked “Genoise”/cake in a humid kitchen cloth or on humid kitchen cooking paper.

Once you have cooked all your Genoise/cakes, it is time to take the Ganache/frosting out from the fridge. (The colder your Ganache will be, the easier for you to whisk it and double the volume afterwards)
With an electric mixer, whisk your Ganache until it doubles of volume.

Arrange the cake :

On a serving tray, add the purple cake, and coat it with your whisked Ganache. Then add the blue cake and coat it with the whisked ganache. Do the same with the green, yellow, orange and red cakes.

Then, coat the top and the side of the cake with the rest of the Ganache. Leave it to chill for an hour minimum (so the ganache will become a bit harder)

Finally, you can decorate as you wish ! and it is ready to be served !!!
Don’t forget to take pictures of it as after so many hours of cooking, you WANT to show of to everyone at the office 🙂

Below a few pictures of how I decorate my table. I bought those little thin vases and added food coloring into each of them before putting my flowers. For the guests, I bought smaller glass vases,  added M&Ms in each of them, and the name tag (written with the rainbow colors of course !) My eldest daughter even did the letters of her sister with her rainbow loom ! (see pictures above) . I used a rainbow stripped  candy and form it into a 8.
IMG_5798 IMG_5795IMG_5793


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