Cut the top of the cake so it is level.
Cut the cake in half.
Top of half of the cake with a layer of buttercream.
Place the other half of the cake on the top of the other cake.
Stand the cake up on its side so the cut side is now the bottom.
Cover the whole cake with a layer of buttercream and smooth it out so the edges are rounded.
Press the coconut into the buttercream of the cake to create the bunnies fur.
Cut a marshmallow in half and dip the sticky side of the marshmallow into the sugar.
Press the marshmallows into the top front of the cake for its ears.