1Heat oven to 350°F (325°F for dark or nonstick pans). Place paper baking cup in each of 24 regular-size muffin cups. Make and bake cake mix as directed on box for 24 cupcakes. Cool in pan 10 minutes; remove from pan to cooling rack. Cool completely, about 30 minutes.
2With end of round handle of wooden spoon, make deep, 1/2-inch-wide indentation in center of each cupcake, not quite to the bottom (wiggle end of spoon in cupcake to make opening large enough). In small bowl, mix 1 cup vanilla frosting and the marshmallow creme. Spoon into small resealable food-storage plastic bag. Cut 3/8-inch tip off 1 bottom corner of bag. Insert tip of bag into each cupcake and squeeze bag to fill.
3In small microwavable bowl, microwave chocolate frosting, chocolate chips and corn syrup uncovered on High 30 seconds; stir. Microwave 15 to 30 seconds longer; stir until smooth. Dip top of each cupcake into frosting. Let stand until frosting is set.
4Spoon 3 tablespoons vanilla frosting into small resealable food-storage plastic bag. Cut tiny tip off 1 bottom corner of bag. Pipe initials or a squiggle shape on each cupcake. Store loosely covered.