Prepare brownie mix according to package directions and cool completely. Cut into 1 inch squares.
In a large bowl, combine pudding mix, water and sweetened condensed milk. Mix until smooth, then fold in 8 oz of Cool Whip until no streaks remain.
In a trifle bowl or glass serving dish, place 1/2 of the brownies, 1/2 of the pudding mixture and 1/2 of the 12 oz container of Cool Whip. Repeat Layers. Shave candy bar onto top layer for garnish. Refrigerate 8 hrs before serving.