1 sheet puff pastry (about 1/2 lb.)
1 4 oz. chocolate bar
1 egg + 1 Tablespoon water
Powdered sugar — for dusting
Prepare a baking sheet lined with parchment paper. Set aside.
On a lightly floured surface, place puff pastry and roll out slightly with a floured rolling pin. Cut into 9 (5-inch) squares.
Cut or break up chocolate bar into 9 (1 inch x 1/2 inch) pieces.
Whisk egg and water in a small bowl, until well combined. Set aside.
Place 1 chocolate piece at the bottom of each pastry rectangle. Fold pastry over the chocolate. Lightly brush egg wash on the remaining dough and fold over again to seal. Place seam side down on your lined baking sheet.
Lightly brush each pastry with egg wash. Refrigerate tray for at least 10 minutes (up to 12 hours) to firm up.
When ready to bake, preheat oven to 400°. Bake for 10-12 minutes, until golden brown and puffed. Allow to cool for about 10 minutes, then dust with powdered sugar.