Make Duncan Hines yellow cake in two round 9" cake pans. Bake as usual. Cool. Cut layers in half with a thread to made four thin layers total. Mix together: 2 C. sugar, 2 C. coconut, 2 C sour cream. Setting one cup of mixture aside, ice in between all layers, and put a little bit on top. Mix the remaining cup of the mixture with 12 oz. Cool-Whip and ice entire cake (outside and top). Important: Refrigerate three days in covered container. I use a large Tupperware Cake Saver.