In a large bowl, combine margarine, sugar, cocoa, flour, baking powder, salt, vanilla and nuts. Stir with fork, DO NOT USE MIXER. Pour batter into a greased 9 x 9 inch glass dish.
Combine 1/2 cup brown sugar, 1/2 cup white sugar, 1 cup hot water and 2 tablespoons cocoa. Whisk well. Add 1 teaspoon vanilla. Pour over batter in pan. DO NOT STIR. Bake at 350 for 35 minutes. Serves 6. Serve with vanilla ice cream.
Note: DO NOT try to remove this cake from the pan, as the bottom is full of sauce and you WILL have a NASTY MESS if you dump it out.