Sunday, 15 July 2012

Strawberry Milkshake Rainbow Sponge

Last weekend my friend Beth celebrated her birthday with a children's party, which gave me the perfect excuse to make the rainbow cake I've been thinking about. Although this takes a lot of timely and careful preparation, the recipe itself is incredibly simple.

You will need six 6" square cake tins and six bowls for mixing (small bowls will do). If you have fewer tins, you can re-use them. I used one of these marvellous adjustable tins.

For the sponge:
12oz/330g margarine
12oz/330g caster sugar
6 eggs
12oz/330g self raising flour
3 tsp baking powder
6tsp vanilla extract
6tsp strawberry flavouring
1/2 tsp each of gel food colourings - red, orange, yellow, green, blue and purple

 For the internal buttercream:
(recipe courtesy of Mary-Anne at Time to Cook Online)
This is lighter and less sickly than standard buttercream.
250ml milk
4 tbs plain flour
225g unsalted butter
225g caster sugar
1 tsp pure vanilla extract

For the external buttercream:
This gives a sturdier buttercream for the outside of the cake.
200g unsalted butter
200g icing sugar
1tsp vanilla extract
1tsp strawberry flavouring

To decorate: An assortment of rainbow-coloured children's sweets. The ones on this cake are all suitable for vegetarians (no gelatine or cochineal).

1. Grease and line your tins. Pre-heat the oven to 180 degrees celcius.

2. In each of your bowls, cream together 2oz/55g margarine with 2oz/55g sugar until light (almost white) in colour.

3. Beat togther one egg with one of the colourings, and gradually mix in to one portion of creamed butter and sugar. If the mixture starts to curdle, add in a little of the flour.

4. Repeat this process, adding coloured egg to as many of the bowls of cake mixture as you will be able to bake in the first batch.

5. Stir in 2oz/55g flour and 1/2tsp baking powder into each of the batches that are ready to be baked, adding 1tsp each of vanilla extract and strawberry flavrouing at the same time.

6. Put each prepared portion of cake mixture into one of the prepared tins and bake for 15-20 minutes at 180 degrees celcius.

7. Allow the baked cakes to cool thoroughly on a cooling rack. Meanwhile, start preparing the internal buttercream. Whisk together the milk and the flour in a pan on the hob until the mixture thickens. Continue cooking and stirring for another minute to cook out the flour.

8. Pour the mixture onto a plate and cover closely with clingfilm so that a sking does not form. Allow to cool completely.

9. Beat together the sugar and butter until creamy and pale in colour. Add the milk mixture when it is completely cooled, and the vanilla extract. Continue wisking until the mixture is pale and thick.

10. Sandwich together the six layers of cake with the internal buttercream, starting with the purple on the bottom, and working up to a red top layer.

11. Prepare the external buttercream: Whisk together the butter and icing sugar until very light and pale in colour. Whisk in the vanilla extract and strawberry flavouring.

12. Cover the outside of the cake with the external buttercream and decorate with the colourful sweets.

Try and keep the exciting insides a secret, and wait for the gasps of excitement when the recipient finally cuts the cake!


  1. Thank you very much! I felt like a kid at Christmas, making this!

  2. OMG! Are those little meerkats on the side? Haha...this is what impressed me apparently, not the cake, because really, I didn't expect anything less ;-)

    1. Meerkats indeed... one of the few jellyish sweets that are veggie-proof and hence a firm favourite of Beth and myself. Now available in Morrisons of all places!

  3. How many does this serve?

    1. Sorry for the late reply... only just noticed the post. This cake comes out as a 6 inch cube, so it will feed 15 people easily, and I would say up to 20 without too much hassle. It's so tall that you only need quite small pieces. In fact, at the party above, quite a few people only took slices that were 3 layers deep. Hope that helps, and good luck with it!

    2. Thanks P, that really helps :) Now I can scale up as necessary. I take it each layer comes out one inch deep then?

  4. Yes, roughly an inch depth per layer! Good luck and let me know how the scaling up goes!

    1. Just to clarify, the layers are a little less than an inch, and make up to an inch ish with the buttercream