Let pie crusts stand at room temperature for 15 minutes. Preheat oven to 400°F. Lightly coat twelve 2-1/2-inch muffin cups with cooking spray. For pastry shells, unroll pie crusts. Use a 3-1/2-to 4-inch round cutter to cut 6 rounds from each crust. Press rounds into prepared muffin cups, pleating to fit.
For filling, in a medium bowl stir together berries, cornstarch and lemon juice. Spoon berry mixture into pastry shells. Bake for 20 minutes or until pastry is golden. Cool in muffin cups on a wire rack for 5 minutes. Carefully remove tartlets from muffin cups; cool completely on wire rack.
In a medium mixing bowl combine whipping cream, lemon curd, 1 teaspoon sugar, and vanilla; beat with wire whisk or with electric mixer on medium speed until cream mixture mounds and is fluffy. Spoon on tarts. Garnish each tart with a mint sprig.