Preheat oven to 375°. Grease and flour 2 (9-inch) pans. Melt 1/3 cup chocolate bits. Combine graham cracker crumbs and melted butter. Stir in walnuts and rest of chocolate bits. Cream 1/2 cup of butter. Gradually add sugar, cream well, add eggs, one at a time, and beat well. Blend in melted chocolate bits and vanilla. Sift flour, soda and salt. Add alternately with milk at low speed on mixer. Turn batter into pans. Sprinkle tops with graham crackers, buffer, walnuts and chocolate bits mixture. Bake at 375° for 30 to 40 minutes. Frost sides and between layers with a 7-Minute Frosting.