Preheat oven to 400°F. Place pastry shells onto a parchment-lined baking sheet. Bake until golden brown and raised, 20 to 25 minutes. With a fork, remove pastry shell tops and soft pastry below to form a well. Return bottoms to oven to bake centers, 4 to 5 minutes. (Reserve tops for another use. Shells can be baked 1 day ahead; reheat for 3 to 5 minutes at 375°F).
Mix berries with 1 Tbsp. confectioners' sugar and lemon juice. Set aside.
Using an electric mixer, whip cream and remaining 2 Tbsp. sugar until semifirm peaks form, 3 to 4 minutes.
Fill pastry shells evenly with berries. Top with a heaping spoonful of whipped cream and serve.
