Split the mixture evenly between the three tins - bake in the oven for 30-35 minutes, or until baked through! Check with a skewer (it should be clean!)
Leave your sponges to cool in the tin for 10-15 minutes, and then on a wire rack to cool fully!
For the Decoration!
Beat your room temperature unsalted butter for a couple of minutes to loosen it and make it lighter!
Add in the icing sugar a bit at a time and mix in fully!
Add in the vanilla extract, and beat again. If your mixture is really stiff (and I mean, you will not be able to pipe with it - add in 1-2tbsp of boiling water to make it easier to pipe)
Using your favourite piping tip, pipe buttercream onto your sponges, and add each layer of cake as you go!
Once you have piped all of the buttercream on, sprinkle the cake with some more Funfetti Sprinkles and enjoy!