Heat oven to 350°F.
In medium mixing bowl, combine 3/4 c sugar, flour, 3 T cocoa, baking powder and salt.
Blend in milk, melted butter and vanilla; beat until smooth. Pour batter into square pan, 8x8 or 9x9.
In small bowl, combine remaining 1/2 c sugar, brown sugar and remaining 4 T cocoa powder; sprinkle mixture evenly over batter. Pour hot water over top; do not stir.
Bake 40 minutes or until center is almost set. Let stand 15 minutes; spoon into dessert dishes, spooning sauce from bottom of pan over top.
8 servings