PREPARE cake batter as directed on package. Stir in dry jelly power until well blended.
LINE 24 medium muffin cups with paper liners. Pour batter evenly into cups, filling each cup half full. Place a small marble or 1/2-inch ball of foil between each liner and side of cup, pushing the paper in to form a heart shape. Bake as directed on package for cupcakes. Cool completely; remove marbles or foil.
SPREAD 2 Tbsp. of the whipped topping onto top of each cupcake. Decorate with sprinkles as desired. Store in refrigerator.
serving size = 1 cupcake (42 g)