Preheat your oven to 400°F (200°C).

Unroll the store-bought puff pastry and slice it into 4-5 rectangles on a lightly floured surface.

Melt your choice of chocolate in a microwave or double boiler until smooth. Mix in vanilla extract and a pinch of salt if desired.

Place about 1 tablespoon of the melted chocolate onto the center of each rectangle, leaving an edge for sealing.

Fold each pastry over the chocolate filling and press down the edges to seal. Crimp the edges with a fork for decoration.

Brush the tops with the beaten egg and sprinkle a bit of sugar on top if desired.

Bake on a lined baking sheet for 20-25 minutes, or until golden brown and puffed.

Allow to cool on a wire rack and dust with powdered sugar before serving, if desired.