Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
On a lightly floured surface, roll out each sheet of puff pastry to smooth out creases. Cut each sheet into 4 equal squares.
In a small bowl, mix the chocolate chips with the vanilla extract.
Place about 2 tablespoons of the chocolate mixture in the center of each pastry square.
Fold the corners of each square towards the center to create a pocket, pinching the edges to seal well.
Brush the tops of the pastries with the beaten egg. If desired, sprinkle with granulated sugar for added sweetness and crunch.
Bake in the preheated oven for 15-20 minutes or until golden brown and puffed.
Remove from the oven and let cool slightly. Dust with powdered sugar if desired before serving.