Heat oven to 350°F. Prepare cake mix according to package directions. Pour batter into two 9-inch heart-shaped pans. Bake 30 minutes, or until a wooden pick inserted in center comes out clean. Transfer pans to wire racks and cool 10 minutes. Remove cakes from pans and cool completely on racks.
Place 1 cake layer, flat-side-down, on a platter. Spread 1/2 cup frosting over surface. Place second cake layer, rounded-side-up, over frosting. With a small knife, cut out a 3/4-inch-deep heart shape. Leave a 1-inch border on all sides. Discard (or eat) cake removed from center. Frost sides and top border of cake with a very thin layer of frosting to seal in crumbs (see note). Refrigerate 20 minutes. Frost cake with another thin layer of frosting. Wrap fruit strips neatly around sides.
Place Necco wafers around cake bottom, tucking them halfway under cake to form a scalloped edge. Place red candy hearts over wafers. Arrange chocolates (in their wrappers) in center of cake.
Bakers call this technique a crumb coating. It is most useful when covering a dark cake with light frosting because it prevents dark crumbs from mixing into the top layer of frosting.