Use the milk to make your pudding.
When cake is cool, cut into 1-inch squares.
Assemble the trifle either in a trifle bowl or in a large glass bowl by putting a layer of cake, a layer of Cool Whip, a layer of chocolate pudding, a layer of caramel ice cream topping, and last a layer of Heath brickle. Repeat this order until you have filled the bowl, ending with the brickle.
Refrigerate until ready to use.