Set oven to 350. Stir together ¾ c. sugar, flour, 3 T. cocoa, baking powder and salt. Stir in milk, butter and vanilla, mixing until smooth. Pour batter into an 8" square glass pan. Mix ½ c. sugar, brown sugar, and 4 T. cocoa. Sprinkle evenly over batter. Pour hot water over top. Do not stir. Bake 35 to 40 min or until center is almost set. Let stand 15 min. then serve. Can use chocolate syrup from bottom of dessert to spoon over servings. Serve with ice cream.