Preheat oven to 350 degrees F. Grease 8 x 8 x 2-inch-square baking pan. Line bottom with waxed paper; grease paper. Lightly dust pan and paper with flour (or graham crumbs).
Begin melting butter in large, heavy saucepan over medium heat. When half melted, remove from heat. Stir in chocolate. Stir until mixture is melted. Stir in sugar, graham crumbs, 1 cup marshmallows and vanilla. Stir in eggs.
Pour batter into prepared pan.
Bake in preheated 350 degree F oven 30 minutes. Sprinkle remaining 1/2 cup marshmallows over top. Bake 10 minutes. Cool torte in pan on rack 20 minutes. Run knife around edge of cake; cover with waxed paper; invert onto plate. Remove pan; peel off lining paper. Cover with rack; invert. Remove waxed paper. Cool torte completely on rack. Makes 12 servings.