Prepare brownie mix according to package directions
Pour into a 13 x 9 in. pan and bake according to package directions
Prick the top of warm brownies at 1 in. intervals with a wooden toothpick and brush with coffee liqueur, if desired.
Crumble brownies into small pieces.
Crush candy bars and set aside
Prepare pudding mix according to package directions without chilling.
Place half of crumbled brownies in bottom of a 3 qt. trifle bowl; top with half each of pudding, candy bars, and whipped topping
Repeat layers. Cover and chill at least 8 hrs.