Split each cake into two sponges, so you have four layers.
Using a 10" cake board, add your first layer.
Add a couple tablespoons of the buttercream on to the sponge and smooth over. Add a couple of spoons of jam to the middle.
Repeat with the second and third layers, and then add the last layer on top.
Using the leftover white buttercream, smooth over the sides of the cakes and fill in any gaps and create a crumb coat.
Refrigerate or freeze the cake on the board for an hour or so to chill and firm to make the next stage of decorating easier.
Once chilled, using a spatula or small piping bags, pipe the colours of buttercream around the sides of the cake.
Smooth over using a large metal scraper until the sides of the cake are smooth like in the photos! You may need to add in more buttercream as you go to get the finish you want but this is totally normal!
Once this has been done, refrigerate again whilst you make the drip!
Add the white chocolate and double cream to a bowl and heat in a microwave in short 10 second bursts stiring well each time.
Once melted and combined, add the white food colouring and mix until smooth!
Add the ganache to a piping bag and carefully cut off the end and drip down the sides of the cake. The more you push over the side of the cake with the piping bag, the further it will drip!
Add the leftover buttercream to a piping bag by adding lines of each colour onto a large piece of clingfilm and rolling this into a sausage.
Snip the end off of this, and add to a large piping bag with your favourite piping tip and pipe swirls of buttercream onto the top of the cake.
Finally sprinkle on some sprinkles and leave the cake to set in the fridge fully.
In the hot weather I store the cake in the fridge until it has been portioned.
This cake lasts 4-5+ days once made!
The colours that you use and what order are up to you, this recipe is just how I did it! You can swap up the order or whatever you prefer!
You should avoid supermarket colours as they are not strong enough.