Grease a 9-inch square baking dish or pan. Heat oven to 350 degrees F.
Into large bowl, sift together flour, sugar, 2 tablespoons cocoa, baking powder
and salt. Stir in milk and melted margarine. Blend in walnuts. Spread in prepared
dish. Sprinkle brown sugar and 1/4 cup cocoa over batter in dish. Pour hot water
over entire batter.
Bake for 35 to 40 minutes or until batter is set and sauce bubbles.
Let cool before slicing. (It makes its own chocolate sauce.)
Enjoy with vanilla ice cream or whipped cream, if desired.