Heat oven to 450°F. Lightly spray cookie sheet with cooking spray. Remove pie crust from pouch; unroll on cookie sheet.
In medium bowl, mix 2 tablespoons granulated sugar and the cornstarch. Gently stir in 3 cups of the strawberries. Spoon onto center of crust, spreading to within 2 inches of edge. Fold 2-inch crust edge up over filling, pleating decoratively. Brush crust edge with water; sprinkle with 1 teaspoon granulated sugar.
Bake 15 to 20 minutes or until crust is golden brown.
Meanwhile, in small bowl, beat whipping cream and powdered sugar with electric mixer on high speed until stiff peaks form. In another small bowl, mash remaining 1/4 cup strawberries; fold into whipped cream. Serve tart with strawberry whipped cream. Garnish with fresh mint.