1Heat oven to 350°F (325°F for dark or nonstick pan). Place Reynolds Baking Cups in each of 24 regular-size muffin cups. Make and bake cake mix as directed on box for 24 cupcakes. Cool in pans 10 minutes; remove from pans to cooling rack. Cool completely, about 30 minutes.
2Meanwhile, place 12-inch sheet of waxed paper on cookie sheet; mark an 8-inch square on waxed paper. Alternately place spoonfuls of melted chocolate and butterscotch on waxed paper. With small spatula, swirl together for marbled effect, spreading to an 8-inch square. Refrigerate until firm, about 30 minutes.
3Remove from refrigerator; let stand about 10 minutes or until slightly softened. Use 1 1/2-inch leaf cookie cutter to make 24 leaf cutouts. Carefully remove cutouts from paper with spatula; place on another waxed paper-lined cookie sheet. Refrigerate until firm, about 5 minutes.
4Frost cupcakes. Garnish with leaf cutouts. Store loosely covered in refrigerator.