Cream shortening and sugar, then beat in egg. Combine flour, baking soda, and salt. Gradually add to creamed mixture and mix well. Dough will be stiff. Stir in apples. Spread into a greased 9x13-inch pan. Combine brown sugar, walnuts, cinnamon, and vanilla. Spread over top. Bake at 350 degrees for 30–35 minutes or until golden brown.