Prepare and bake the cake as directed on the package. Allow to cool. Remove from pan. Slice a 1 inch layer off the top. Gently hollow out a trench about 1 1/2 inches wide and 2 inches deep. Tear the removed cake into small pieces and set aside.
In a medium bowl, combine milk and pudding mix. Beat on low for 2 minutes. Fold cake pieces and 1 3/4 cups of whipped topping into pudding. Fill trench with pudding mixture. Replace top of cake. Spread remaining whipped topping over top and sides of cake.
