1 Heat oven to 350°F (325°F for dark or nonstick pans). Grease bottoms and sides of two 8-inch round cake pans and a 13×9-inch pan, or spray with baking spray with flour. In large bowl, beat 1 cake mix, 1 cup of the water, 1/2 cup of the oil and 3 eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Pour into round pans, dividing batter evenly. Bake as directed n box for 8-inch round pan. Cool cakes in pans 10 minutes; remove from pans to cooling racks. In large bowl, beat remaining cake mix, remaining 1 cup water, 1/2 cup oil and 3 eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, stirring occasionally. Pour into 13×9-inch pan. Bake as directed on box for 13×9-inch pan. Cool cake 10 minutes; remove from pan to cooling rack. Cool completely, about 1 hour. For easier handling, refrigerate or freeze cakes about 1 hour or until firm.
2 Meanwhile, in medium bowl, mix 1 container plus 1 cup chocolate frosting with food color to make black frosting. Cut marshmallow in half crosswise.
3 Using serrated knife, cut off top rounded portion of each cake to level surface. Turn cakes cut sides down. Cut cakes as shown in template. Place cake pieces on tray as directed in template, attaching to tray and to each other with small amount of frosting.
4 Spread thin layer of vanilla frosting over head and thin layer of black frosting over ears, body and paws to seal in crumbs. Refrigerate or freeze cake 30 to 60 minutes to set frosting.
5 Frost head with some of remaining vanilla frosting. Frost rest of cake with some of remaining black frosting. To pipe on panda features, spoon vanilla and black frostings into separate resealable plastic freezer bags and cut small tip off 1 corner of each bag.
6 Pipe or spread vanilla frosting on body to create chest. Pipe or spread black frosting on head for patches around eyes. Place marshmallow eyes on patches. For pupils, attach 1 mint to each marshmallow slice with frosting. Pipe or spread black frosting on snout for nose and mouth. Pipe or spread vanilla frosting on back paws to create paw prints. Pipe outline around body and front legs with black frosting. Fill in outline with additional black frosting so front legs have a thicker layer of frosting than white chest. Using metal spatula, create a different texture on the body and front legs to further define legs from chest and back paws. Store loosely covered.