Set aside 2 tablespoons graham cracker crumbs. In a large bowl, beat the remaining crumbs, cake mix, sugar, water, egg whites and oil for 2 minutes.
Pour into two greased and floured 9-in. layer pans. Bake at 350° for 25-30 minutes or until a toothpick inserted in the center comes out clean. Let stand a few minutes before removing from pans to wire racks to cool completely.
Cut each cake horizontally into two layers. Place bottom layer on a serving plate. Spread whipped cream between layers and frost entire cake. Sprinkle reserved graham cracker crumbs on top. Refrigerate until serving time.