1 lb. puff pastry

1/4 c. grainy mustard

3/4 lb. thinly sliced good-quality ham

3/4 lb. thinly sliced cheddar or swiss cheese

1 egg white, lightly beaten with 1 T. water

If using frozen puff pastry, defrost in the refrigerator for 1 hour before using. Divide the pastry in half and roll half out onto a floured board into a rectangle approximately 12-inches-by-16-inches. With a sharp, wet knife, cut the rectangle into two 12-inch-by-8-inch rectangles.

Spread half of the mustard in a thin layer over one rectangle of pastry, leaving a 1/2-inch border on all four sides. Layer half of the ham evenly over the mustard, then half of the cheese over the ham.

Brush the uncovered pastry border with a bit of cold water, then place the unlayered rectangle of pastry on top. Press the edges together and crimp with your fingers as you would a pie. Prick the surface all over with a fork.

Repeat the assembly process using the remaining pastry, mustard, ham and cheese. This dish may be made ahead and refrigerated at this point.

To bake, preheat oven to 400 degrees. Brush the surfaces of the pastry with the egg white mixture to glaze. Place each pastry packet on an ungreased baking sheet and bake for 12-15 minutes, or until the pastry is puffed and golden brown.

Remove from the oven and allow to rest for 5 minutes. Carefully transfer to a cutting board and cut each rectangle into 12 smaller rectangles. Serve immediately.