Preheat oven to 400°F (200°C). Roll out puff pastry sheets and cut into layers. Bake for about 25 minutes until golden brown.

Allow baked pastry layers to cool completely on a wire rack.

Combine mixed berries, granulated sugar, and cornstarch in a saucepan. Cook over medium heat for 5-7 minutes until thickened.

In a mixing bowl, whip heavy cream with powdered sugar and vanilla extract until soft peaks form.

Layer cooled pastry, followed by berry filling and whipped cream, repeating until desired height.

Cover with plastic wrap and chill in the refrigerator for a couple of hours before serving.