To finish the cake: Trim the top to make it flat and slice each layer into two horizontal layers. Then fill the layers with the Italian Buttercream and refrigerate for an hour or two to firm it up.

The chocolate buttercream will stiffen as it sits, so you want to work while the buttercream is freshly made, lightly frost the top and sides of the cake and finish with pretty spatula twirls and patterns. You can ice smooth and then pipe fancy things, but it isn't necessary. If it gets too stiff to work with, beat in a small amount of heavy cream to soften slightly. The more cream you add, though, the softer the buttercream will be.

The finished cake doesn't require refrigeration unless you are making it in hot weather, but keep it cool until serving. After serving, refrigerate the leftovers.