Using a 5" cookie cutter cut a hole in the centre of 2 of the 3 cakes and leave to one side.
Place one of the cakes with the centre removed on your serving plate and pipe the buttercream on top. Smooth using a spatula, don’t worry is any of the buttercream splodges out the side.
Place the second cake with the missing centre on top and pipe the buttercream on top and smooth. Fill the hole in the centre with M&Ms until it is full.
Finally stack the final cake on top.
Pipe the buttercream onto the top of the cake, again don’t worry if it goes over the edges.
Using your cake smoother smooth around the sides of the cake. Don’t worry if you can see the cake through the buttercream, this is just the crumb coat. We will cover the cake soon.
If there are any gaps, pipe buttercream into the gaps and then smooth again using your cake smoother.
Once there are no gaps in your cake pop it into the fridge until the buttercream has hardened.
Once the buttercream has hardened, pipe the remaining buttercream around the sides of the cake
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.
To smooth the top edges of the cake, use a palette knife and smooth any buttercream into the top of the cake.
Pipe some swirls onto the top of the cake and decorate with M&Ms