Melt 3 T. butter add coconut and pecans in a skillet. Stir constantly until mixture is golden brown. Remove from heat and drain on paper towels.
Mix the cake according to directions adding to 1 c of the toasted coconut and pecan mixture. Divide among 3 8-inch pans. Bake,cool according to package directions.
To make the frosting,cream the remaining butter and cream cheese until light and fluffy. Add the milk,vanilla and powdered sugar,beating well until mixture is spreading consistency. Add the remaining toasted mixture minus 1/2 c to sprinkle on top of cake. Fill and frost the cake with frosting.