Mini Croque Monsieur

Ingredients
2 tablespoons butter
2 tablespoons flour
1 cup milk
1 ½ tablespoon whole grain dijon mustard
salt and pepper
1 sheet puff pastry (14 oz)
½ cup ham (diced)
1 cup gruyere (shredded)
1 egg (lightly beaten with water)
Instructions
Preheat oven to 425º. Line cookie sheet with parchment paper.
In a small saucepan, melt the butter over medium heat, add flour and stir constantly for about three minutes, until smooth. Slowly add milk while whisking for about 5 minutes until it thickens. Remove from heat and add mustard. Salt and pepper to taste.
Roll out pastry slightly into a 13 X 15 rectangle and cut into rounds with a 2 inch biscuit cutter. Use a smaller cutter to make a circle inside each round without cutting all the way through. Poke the center with a fork.
Use a pastry brush to brush the edges of the rounds with an egg lightly beaten with a tablespoon of water.
Top each round with about ½ teaspoon of the béchamel, some chopped ham and shredded cheese. (You will have some bechamel left over. Sprinkle pepper on top.
Bake for 15 minutes, or until golden and puffy.