Preheat oven to 350°F. In mixing bowl, combine flour with sugar, nuts, 2 tablespoons cocoa, baking powder and salt. Add vanilla, shortening and milk; mix until well blended. Spread in ungreased 8 or 9-inch square pan. Combine brown sugar, 1/4 cup cocoa and hot water; pour over batter. Bake about 45 minutes or until cake topping is set. Serve warm or cool, topped with cream or whipped cream.