1. Soak the pears in lemon juice to prevent them from turning brown.
2. Preheat the oven to 400°F.
3. Roll out the puff pastry and cut 4 large squares.
4. Place a pear in the center of each pastry square.
5. Fill each cored pear with chocolate chips. Also, place chocolate chips around the pears.
6. Fold the pastry to cover the pears. Seal well above the pear to close the pastry.
7. Brush the beaten egg on the pastry.
8. Place the closed squares on a baking sheet. Bake for 20 minutes or until the pastry is golden brown.
9. Remove from the oven and serve, accompanied by a little custard.