I got this recipe from an acquaintance I met on the internet from Arkansas. I have made this several times and always get requests for it. In fact, when it's time for me to bake for one of my Sunday School gals birthday, one friend always requests I make this cake for her!
Mix sour cream, coconut and sugar and refrigerate for at least 12 hours before preparing cake (I usually do this the day before).
The next day use 1 cup of the coconut/sour cream mixture and mix with the Cool Whip and return both to refrigerator until you are ready to assemble the cake.
Mix cake according to box directions and add 1 can of cream of coconut to cake batter. Mix well. Pour cake batter in two prepared 9-in. cake pans that have been greased and floured. Bake at 350 for 30-35 minutes.
After cake has cooled, place one cake layer on serving plate. Spread the coconut/sour cream mixture on top of first layer. Top with the second cake layer. Frost entire cake with the Cool Whip/coconut mixture and refrigerate for at least 24 hours.