Heat oven to 350°F (325°F for dark or nonstick pan). Grease 13x9-inch pan with shortening or cooking spray. Make and bake brownies as directed on box, using water, oil and egg. With fork, poke holes in baked brownies; pour liqueur over brownies, allowing it to seep into holes. Cool completely in pan.
Meanwhile, in large microwavable bowl, microwave chopped candy and 1/4 cup of the whipping cream uncovered on High 1 minute to 1 minute 30 seconds, stirring after 1 minute, until chocolate is melted. Let stand 45 minutes or until almost cool. In chilled large bowl, beat remaining 1 1/4 cups whipping cream with electric mixer on high speed until soft peaks form. Gently fold whipped cream into chocolate mixture.
Crumble brownies into bite-size pieces; divide evenly among 36 (2-oz) shot glasses. Spoon chocolate cream mixture evenly over brownies. Top each dessert with whipped cream topping. Garnish with sugared cranberries and mint leaves, if desired.