Meanwhile, in 1-quart saucepan, mix sugar and cornstarch. Stir in water and lemon juice until smooth. Add 1 cup of the blueberries. Heat to boiling over medium heat, stirring constantly. Boil about 2 minutes or until thickened; remove from heat. Stir in remaining 1 cup blueberries. Place blueberry topping in small bowl; let stand at room temperature 5 minutes. Cover and refrigerate until chilled.