Preheat your oven to 400°F (200°C).

In a bowl, mix the chopped strawberries, sugar, cornstarch, and vanilla extract. Set aside to let strawberries release their juices.

Roll out thawed puff pastry sheets on a lightly floured surface. Cut each sheet into squares, about 4x4 inches.

Place a spoonful of the strawberry mixture in the center of each pastry square.

Fold the corners of the pastry toward the center, pinching them together to seal.

Place the filled pastries on a baking sheet lined with parchment paper.

Brush the tops with beaten egg for a golden color.

Bake in the preheated oven for 20-25 minutes, or until pastries are puffed and golden brown.

Once done, let them cool slightly before dusting with powdered sugar, if desired.