Preheat oven and bake brownie batter in a 9- x 13-inch baking pan according to package directions Allow to cool completely. Use a fork to prick holes in top of cooled brownies. Drizzle with coffee liqueur. Break up brownies into small pieces. Coarsely crush candy bars in a food processor or by gently tapping the wrapped bars with a hammer.
Place half the brownies in bottom of a trifle dish or large glass serving bowl. Cover with half the pudding then one-third of the crushed candy and half the whipped topping. Repeat layers and top with the remaining crushed candy. Cover and chill at least 2 hours before serving. Refrigerate any leftovers.