Preheat the oven to gas mark 4 or 180 degrees.
Grease and line three 20cm sandwich tins (if you only have two, you will need to reuse one).
In a large bowl, beat together the butter and sugar, then gradually fold in the eggs, self-raising flour and baking powder.
Continue to fold until it forms a smooth cake mixture. Pour into the three tins ensuring each has an even amount. Smooth the top with a spatula.
Bake for 25 minutes. Leave to cool on a wire rack.
Prepare your icing by mixing the icing sugar and butter together until smooth.
Before adding any colouring, use the icing to build your cake. Place a small amount on the cake board to prevent the cake from sliding, and add the first layer. Spread the icing across the cake (optional - add jam), then repeat with the two remaining layers. Spread a thin layer of icing around the sides so that the entire cake is covered with buttercream.
Using your remaining buttercream, add a small drop of food colouring to make a pale pink. Spread this onto the cake (I used a lighter pink at the top). Then add more food colouring and begin spreading this onto the cake. Use the icing scrapr to ensure a clean, smooth finish. I finally added random dots of colour and spread these into the cake with the scraper to give a slightly tie-dye effect.
Place the cake in the fridge to cool.
Prepare your cake drip by placing the whipped cream in a jug in the microwave for 20 seconds. Add the white chocolate (in small chunks) to the cream and microwave for a further 50 seconds.
Stir the mixture and return to the microwave until the white chocolate has completely melted. Add food colouring of choice.
Leave to cool for 5 minutes or so, until the consistency is slightly thicker (as the chocolate cools).
Using a sauce bottle or teaspoon, carefully test the drip on the edge of a mixing bowl. Once it has reached the desired consistency, drip onto the edge of the cake, then spread across the top.
Add your decorations (sprinkles, chocolate, sweets, glitter) then return to the fridge to set.
Remove from the fridge, slice and celebrate!