For cake batter:
- Prepare cake batter and bake in 13 x 9-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 of the cake cubes in large glass trifle bowl.
- Layer half of pudding.
- Layer half of whipped topping.
- Layer half of crushed chocolate bar.
- Repeat all layers.
- Serve immediately or cover and refrigerate until ready to serve.