Crumble 1/2 of cake in large container. Prepare pudding according to directions on package, except using 1 1/2 cups milk per package. Pour 1/2 pudding over crumbled cake. Spread layer of Cool Whip and sprinkle on crushed Heath bar on top of Cool Whip. Repeat layers of cake, pudding, and Cool Whip, then Heath bar.
This is a very large recipe, it may be cut in half.