Preheat oven to 350°. Prepare cake mix according to package directions, baking in two 8-inch baking pans. Cool 15 minutes on wire racks. Remove cakes from pans and cool completely. Trim tops of cakes to flatten. Wrap cakes in aluminum foil and freeze at least 2 hours.
Remove cakes from foil and on serving platter, arrange 1 cake. Scoop Breyers® Ice Cream onto cake, smoothing to form an even layer. Top with second cake, pressing down slightly. Freeze 5 hours or overnight.
Beat whipped topping with marshmallow creme in large bowl with wire whisk until smooth. Frost cake with whipped topping mixture. Freeze 1 hour. Decorate as desired.