Ham and Cheese Hot Pockets

2 Sheets Frozen Puff Pastry (thawed according to package directions)
1/2 lb Black Forrest Ham
1/2 lb Gruyere Cheese, sliced (or Havarti or Muenster)
2-3 T. mustard (yellow, Dijon, or spicy brown)
1 beaten egg
1 tablespoon water

Roll the pastry sheets on a floured surface until they are just smaller than a large cookie sheet. Spread the mustard all over one of the pastries, leaving a one inch border all around. Layer the cheese and ham on top of the mustard. Place the other pastry on top of the layers of cheese and ham and seal the edges all around with a fork, by pressing firmly. Make slits in the top of the pastry with a knife and brush the top pastry with one beaten egg mixed with one tablespoon of water. Bake at 400 for about 20 minutes.