Once the cakes have cooled completely, level and half each cake so you end up with four layers.
Place your first cake on your serving plate and spread the buttercream on top. Smooth using a spatula, don’t worry if any of the buttercream splodges out the side.
Repeat until all four cakes are stacked.
Smooth the buttercream around the sides of the cake and into any gaps. Smooth using a cake smoother. Don't worry if you can still see the cake through the buttercream this is just our crumb coat.
Pop the cake into the fridge for 30 minutes or so until the buttercream has set.
Once the buttercream has set remove the cake from the fridge and spread the remaining buttercream onto the top of the cake. Using a palette knife smooth the buttercream onto the top of the cake and around the sides.
Using your smoother, smooth around the sides, if there are any gaps fill these with the buttercream and continue to smooth around the sides until the cake is smooth. You will most likely take some of the buttercream off the cake if you do pop this back into your bowl.
Smooth the top of your cake using your angled palette knife.
Put the cake back into the fridge for 30 minutes for the buttercream to set.
Any leftover buttercream pop into a piping bag and leave to one side.