Ingredients

Step by step

1. Preheat the oven to 180°C, fan 160°C, gas 4. Grease and line the bases of 6 x 20cm cake tins (or as many tins as you own – ideally at least two).
2. In the bowl of your stand mixer (or in a large bowl and using an electric whisk), cream the butter and sugar for 5-7 minutes until pale and fluffy, stopping to scrape down the sides of the bowl from time to time.
3. In a medium bowl, sift together the flour, baking powder, bicarbonate of soda and salt.
   Tip

   If you don't use colours in baking regularly and don't want to invest in the Sugarflair products you can also use 5 x 10g tubes Dr Oetker gel food colour in ultra violet, sky blue, lime green, sunshine yellow and neon orange and 2.5 tsp Sainsbury's cochineal red food colouring (from a 38ml bottle). These colours still give a good end result but won't be quite as vibrant.
4. Add the vanilla extract, then the eggs, one at a time, to the creamed butter mixture, beating well and scraping down the sides of the bowl after each addition.
5. With your mixer running on low speed, gradually add the buttermilk until just combined. Then, in three batches, add the flour mixture and mix until just combined.

6. Divide the batter equally between 6 small bowls (each one should weigh just about 300g). To colour the batters, take a tiny amount of each paste using a cocktail stick and add to each bowl (you only need to add a very small amount). Fold in the colour gently and efficiently without overmixing until very bright and vibrant, adding more if needed.

7. Spread the batters into the prepared tins and bake for 17-20 minutes. If you only have 2 cake tins, simply do this in batches, washing and relining the tins between baking each batch. Once the sponges have baked, leave them to cool in their tins for 5 minutes before turning them out onto a wire rack to cool completely.
8. While the sponges are cooling, make the cream cheese icing. With an electric whisk, mix together the butter, Philadelphia and vanilla extract in a medium bowl until smooth. Gradually add the icing sugar and continue to whisk gently until thick and smooth, about 2 minutes.
9. To finish the cake, place the purple sponge on a board and spread a thin layer of icing on top. Top with the blue sponge and spread a thin layer of icing over it. Next, take the green and yellow sponges and, using a 9cm cutter, cut out a circle from the centre of each sponge (snack on these – cook's perk! – or discard). Place the green sponge on top of the blue, spread with icing as before, top with the yellow sponge on top, and ice as before. Fill the 'hole' with the Skittles, then place the orange sponge on top and ice as before. Finally, place the red sponge on top. Ice the top and the sides of the cake with a thin layer of icing, then place in the fridge for 30 minutes (to firm up and give a nicer finish), before icing the top and sides generously with the remaining icing.