homemade yellow cake and a boxed red velvet. The yellow cake was awesome for stacking and icing. The boxed cake, not so much. It's funny, before making this cake I never really thought about what buttercream icing was made of. Guess what? It is mostly butter. I almost died when I saw this recipe, but still wanted to try it so I tried to ignore the ingredients and carried on. I simply added a little food coloring and placed white chocolate chips all over to get my 'polkadots'.