Ingredients:
2 tablespoons unsalted butter
3 tablespoons all-purpose flour
2 cups hot milk
1 teaspoon kosher salt
1/2 teaspoon freshly ground black pepper
Pinch nutmeg
12 ounces Gruyere, grated (5 cups)
1/2 cup freshly grated Parmesan
8 croissants
Dijon
8 ounces honey ham, sliced but not paper thin
Directions:
Preheat the oven to 400 F.
Melt the butter over low heat in a small saucepan and add the flour all at once.
Stir with a wooden spoon for 2 minutes.
Slowly pour the hot milk into the butter–flour mixture and cook.
Whisk constantly until the sauce is thickened.
Remove from heat.
Add the salt, pepper, nutmeg, 1/2 cup grated Gruyere, and the Parmesan.
Set aside.
Slice the croissants in half.
Place the slices on a baking sheet and bake for 4 minutes.
Turn each slice and bake for 2 minutes more, until toasted.
Lightly brush half the croissant with mustard.
Add a slice of ham to each.
Sprinkle with half of the remaining Gruyere.
Top with another piece of toasted bread.
Slather the tops with the cheese sauce.
Sprinkle with the remaining Gruyere.
Bake sandwiches for 5 minutes.
Turn on the broiler and broil for 3 to 5 minutes, or until the topping is bubbly and lightly browned.
Serve hot.