Thaw the pastry at room temperature for about 20 minutes, until it is bendable but still cold.

Preheat the oven to 400 degrees F.

Break chocolate into 12 small rectangular pieces.

Separate egg. Whisk yolk with 1 tablespoon water in a small bowl.

Using a plastic knife, cut puff pastry into 12 squares.

Place chocolate on one edge of pastry and roll tight. Seal open ends with a fork.

Place each roll seam down on a baking sheet that is either well-greased OR lined with parchment paper, or a silicon baking mat.

Brush the tops of the pastry with egg wash.

Bake for 20 minutes until puffed and golden brown.

Let cool, then enjoy!