Preheat over to 350°F. Spray a 9 inch square baking dish with cooking spray. Set aside.
In a large bowl combine ¾ cup granulated sugar, flour, ¼ cup cocoa powder, baking powder, and salt. Stir in the milk, melted butter, and vanilla. Using hand mixer, beat mixture until smooth.
Pour the batter into the 9 inch baking dish.
In a small bowl combine the remaining ½ cup granulated sugar, remaining cocoa powder, and the brown sugar. Sprinkle this mixture evenly over the batter.
Pour the hot water overtop. Do not stir!
Bake for 32-35 minutes or until center is almost set. Remove from the oven and let stand for 10 minutes.
Serve in individual dishes. Top with ice cream or fresh whipped topping.