Meanwhile, in 2-quart saucepan, beat sugar, cornstarch, water and lemon juice with whisk. In small bowl, mash 1 1/2 cups of the sliced strawberries with bottom of whisk or fork to make 1 cup finely mashed strawberries; stir into pan. Cook over medium heat, stirring constantly, until mixture thickens and boils. Boil and stir one minute. Pour into medium bowl; cool 5 minutes. Stir remaining sliced strawberries into cooked strawberry mixture.