Prepare brownie mix according to package directions in a 13- x 9-inch pan. Prick tops of warm brownies at 1-inch intervals with a wooden pick, and brush with coffee liqueur, if desired. Crumble into small pieces.
Prepare pudding mix according to package directions, omitting chilling.
Place half of crumbled brownies in bottom of a 3-quart trifle bowl; top with half each of pudding, candy bars, and whipped topping. Repeat layers. Cover and chill at least 8 hours.
Note: For testing purposes only, we used Kahla for coffee liqueur.