Heat oven to 350°.
In ungreased square pan, 9 X 9 X 2 inches, stir together flour, granulated sugar, 2 tablespoons cocoa, the baking powder and salt.
Mix in milk, oil and vanilla with fork until smooth.
Stir in nuts.
Spread evenly in pan.
Sprinkle with brown sugar and 1/4 cup cocoa.
Pour hot water over batter.
Bake 40 minutes.
While warm, spoon into dessert dishes and top with ice cream.
Spoon sauce from pan over each serving.