Preheat oven to 425 f. Take your puff pastry out and allow to thaw for a few minutes, until you can unfold. Cut pastry into approx. 1.5" squares. Place a square of chocolate onto half of the pastry squares and push down gently. Place another square of pastry on top and cover chocolate. Crimp edges with fork. Beat egg and use a pastry brush (or your finger tip if you don't have one!) to brush the tops of each pie, and sprinkle sugar on the tops. Bake in oven for 10-15 minutes until golden brown and puffed up. Remove from oven, allow to cool.