Preheat oven to 350 degrees F.
In a medium bowl, combine flour, sugar, milk, cocoa, oil, baking powder, vanilla and salt. Batter will be very thick -- don't fear. You might need to stir with a metal spoon.
Spread batter into a greased 9" pie plate or square pan (*Note: make sure your pan has tall sides, otherwise your cake might run over a bit.)
Combine brown sugar and ¼ cup cocoa. Spread over batter.
Top with hot water. Bake for about 30-35 minutes until top is dry and puffed. (*Note: put a cookie sheet underneath your pan in the oven, just in case a little spills over).
Serve warm with ice cream.
