In a large bowl, cream the butter and sugar. Add eggs; mix well. Combine graham cracker crumbs, flour, baking powder, cinnamon and salt; add to creamed mixture alternately with milk and mix well. Fold in apples and 3/4 cup walnuts.
Spread into three greased 8-in. round baking pans. Bake at 350° for 25-30 minutes or until a toothpick inserted in the center comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
Beat cream and confectioners' sugar until stiff peaks form; spread between layers and on top of torte. Sprinkle with remaining walnuts.