In a medium bowl, combine flour, sugar, 2 tablespoons cocoa, baking powder, and salt.
Stir in the milk, oil, and vanilla until smooth. Spread in an ungreased
9-inch square baking pan. Combine brown sugar and remaining cocoa; sprinkle over
batter. Pour hot water over all; do no stir. Bake at 350 degrees F. for 35-40
minutes. Serve warm.