Preheat oven to 350 degrees. Sift together flour, baking powder, salt, granulated sugar and 2 tablespoons cocoa. Stir in milk, margarine or butter, vanilla and nuts. Turn into a 9-inch square pan.
In a small bowl, mix the brown sugar and 1/4 cup cocoa, sprinkle over the top of brownies and carefully pour the hot water over the entire batter. Bake approximately 45 minutes, or until top is set. During baking, the brownies will rise to the top of the pan while the chocolate sauce settles to the bottom. Remove from the oven and cool slightly. Serve while still warm.
Nutrition information per serving: