In a large bowl, combine the flour, sugar, baking powder and salt. In a small bowl, whisk the butter, eggs, milk and vanilla. Stir into dry ingredients just until moistened; set aside. In a small bowl, combine topping ingredients.
Spread half of batter into a greased 13-in. x 9-in. baking dish. Sprinkle with half of the topping. Carefully spread remaining batter over top; sprinkle with remaining topping.
Bake at 375° for 25-30 minutes or until a toothpick comes out clean. Serve warm. Yield: 12-15 servings.