PREPARE cake batter and bake in 13x9-inch baking pan as directed on package. Cool completely on wire rack. Cut into 1/2-inch cubes.
ADD milk to dry pudding mix in medium bowl. Beat with wire whisk 2 minutes or until well blended.
LAYER half each of the cake cubes, pudding, whipped topping and crushed chocolate bar in large glass trifle bowl. Repeat all layers. Serve immediately or cover and refrigerate until ready to serve.
serving size = 1/2 cup