on racks for 10 minutes. Remove from pans and cool completely on the racks. Place one cake layer on serving plate. Spread with Sour Cream / Chocolate Frosting. Top with second cake layer. Frost sides and top of the cake with the remaining Sour Cream/Chocolate Frosting. SOUR CREAM/CHOCOLATE FROSTING: Combine the softened butter or margarine, confectioners' sugar, and sour cream in a mixing bowl; blend well. Add chocolate which has been melted and cooled and vanilla. Beat until smooth. NOTE: I have seen reference to people having trouble with their layer cakes and how they rise. Try this little trick when making this cake. Take the layer that has the least amount of rise on the top and trim it to be flat with a sharp knife. Place the trimmed side down (layer should be upside down). Then frost between layers and place the other layer on right side up and finished frosting. It will give the illusion of having a cake with only one domed layer and will sit better on your cake plate. Also the trimmings are great eating just plain for the cook or for the kids.