Sauté sliced strawberries and balsamic vinegar over medium-high heat for about 3 minutes. Stir in sugar.
In a separate bowl, combine water and cornstarch. Add to pan with strawberries. Bring to a boil. Cook one minute, stirring constantly. Remove from heat – mix in lemon juice. Allow to cool completely.
Arrange small strawberries stem-side down in crust. Pour cooked strawberry mixture over top. Cover and chill for 4 hours.
Top with whipped topping before serving.