To frost a cake with a thick frosting like butter cream, start with a frozen cake if possible. The frozen cake will prevent crumbs from getting into the frosting. If you can’t freeze the cake, spread a super-thin layer of butter cream over the top and sides of the cake and allow the frosting to form a crust. Take your fresh frosting and spread a thicker layer on the top first, working down over the sides. When the cake is frosted, you can smooth the frosting with a flat icing spatula dipped in very hot water. Shake the excess water off and run the spatula over the bumpy icing. Voila! A beautifully iced cake!