1Heat oven to 350°F. Make and bake brownie mix as directed on box for 9-inch square pan, using water, oil and eggs. Cool completely in pan on cooling rack.
2Meanwhile, in medium bowl, mix cherries and kirsch. Let stand at least 20 minutes, stirring occasionally.
3In medium microwavable bowl, microwave hot fudge topping uncovered on High about 1 minute, stirring once, until softened. Fold in 1 container whipped topping until blended.
4Cut brownies into 1 1/2-inch pieces. In 4-quart trifle bowl or glass serving bowl, layer half of the brownie pieces and 1 1/2 cups of the cherries with liquid. Spoon chocolate whipped topping mixture over cherries. Repeat with remaining brownie pieces, cherries with liquid and plain whipped topping. Cover; refrigerate until serving. Shave 1 oz bittersweet chocolate. Sprinkle over trifle. Store covered in refrigerator.