Before frosting a cake, cool it completely, unless the recipe says otherwise. Partially freeze a crumbly cake. Trim any uneven places with a serrated knife. Choose a flat plate 2 inches wider than the cake on all sides. Put a dollop of frosting on the plate and center the cake on top. Set the plate on a lazy Susan, if you have one.
Spread frosting between layers and let it set before coating the top and sides. If you are using a cream filling, spread each cake layer first with a thin coating of melted and strained jelly or preserves (to keep filling from soaking in). Spread filling to within 1/4 inch of the edges. Refrigerate the filled cake for 2 hours before frosting it.
To coat a cake with a thick frosting, spread a thin layer all over and let it set. Then refrost the cake, working up the sides first, finishing with the top. Use a metal spatula, dipping it in hot water to get a smooth finish.
To apply thin frosting to a sponge, chiffon, or angel food cake, pour it evenly over the top and let it run down the sides. On a firmer cake, spread the sides and top quickly; dip the spatula in hot water and smooth the surface. Basic butter cream frosting Cream 1/3 cup butter or margarine until fluffy. Beat in 1 pound sifted confectioner’s sugar, alternately with 5 tablespoons light cream or milk. Add 2 teaspoons vanilla and 1/4 teaspoon salt. To thin, add a little cream; to thicken, add sugar.
Fills and frosts two 8- or 9-inch layers or 24 cupcakes. Chocolate butter cream: Add 1/2 cup sifted cocoa with the sugar. Citrus butter cream: Substitute orange or lemon juice for the cream; omit vanilla. Add 3 to 4 teaspoons finely grated orange or lemon rind. Ornamental icing Beat 2 egg whites and 1/4 teaspoon cream of tartar until foamy. Gradually add, then beat until thick, 3 cups sifted confectioner’s sugar. If too thick to spread, add a few drops of hot water. Dries hard and glossy; makes enough to frost an 8- or 9-inch cake.