Prepare the cake according to directions, making two 8-inch layers. Split both layers horizontally, after they have cooled. Blend together the sugar, sour cream and coconut and chill. Spread all but one cup of the sour cream mixture between the four layers. Blend the remaining cup of the mixture with the whipped topping and spread on the top and sides of the cake. Seal in an air tight container and refrigerate for three days before serving. Keep refrigerated after cutting.
Cajun Country -- New Iberia, Louisiana