Heat oven to 350 degrees. In medium mixing bowl, combine 3/4 cup sugar, flour, 3 tbsp cocoa, baking powder and salt. Blend in milk, melted butter and vanilla; beat until smooth. Pour batter into square pan, 8 x 8 x 2" or 9 x 9 x 2". In small bowl, combine remaining 1/2 cup sugar, brown sugar and remaining 4 tbsp cocoa; 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. Garnish as desired.