1Heat oven to 350°F (325°F for dark or nonstick pan). Line bottom and sides of 9-inch square pan with foil. Grease bottom only of foil with shortening or cooking spray. Make brownies as directed on box for 9-inch square pan. Cool completely, about 1 1/2 hours.
2Using foil to lift, remove brownie from pan. Remove foil. With deep 3-inch heart-shaped cookie cutter, cut 8 brownies.
3Arrange brownies on serving plate. With small strainer, sprinkle brownies and plate with cocoa.