Preheat your oven to 170ºC/150ºC Fan, and line two 6" deep cake tins with parchment paper.
Add the unsalted butter and caster sugar to a bowl, and beat until light and fluffy.
Add in the flour, eggs and vanilla extract and beat again until a lovely smooth cake mixture is formed.
Split evenly between the two tins and bake in the oven for 35-45 minutes (or until a skewer comes out clean!)
Once baked, leave to cool in the tin for 10 minutes, and then leave to cool fully on a wire rack.
Buttercream
Beat the unsalted butter on its own for a while in your mixer until its smooth and supple.
Add in your icing sugar a little at a time and beat fully until its light and fluffy and add the vanilla extract and white food colouring!
(If the mixture is really stiff, add in 1-2tbsp of boiling water and beat fully to smooth out)
Add a small spoonful of the buttercream to a bowl and colour this to a pale pink. Repeat again with another small spoonful and colour this aqua. (You can of course use whatever colours you want.)
Decoration
Level the cakes off if necessary. Split the two cakes into two so you have four layers in total
Add your first cake to a cake board or flat serving plate and secure with a small amount of buttercream.
Spread some buttercream onto the first layer, add the second sponge. Repeat until you reach the top layer of cake.
Spread some buttercream around the sides to fill in the gaps and create a crumb coat. Refrigerate the cake for at least 30 minutes.
Once chilled, carefully dab on the coloured buttercream, and then smooth around using a large metal scraper. You really do not need much coloured buttercream to get the effect.
Refrigerate the cake for another 30 minutes.
In a small bowl or jug, add the white chocolate and double cream and melt carefully in short bursts in the microwave, stirring well each time, until smooth.
Carefully pipe this onto the cake to create a drip - I chose random sections to make the look of the cake. Set the cake in the fridge for another 30 minutes.
I then used some gold paint to paint on to the ganache drips, and then flicked a little gold paint onto the white parts of the cake.