These appetizer-size sandwiches were served at the Julia Child 100th Birthday Celebration held at the Consulate General of France in New York by Les Dames d'Escoffier of New York (LDNY) and the American Institute of Wine & Food (AIWF).
Melt the butter in a saucepan over medium heat. Add the flour and stir until no longer raw, for about 1 minute. Slowly pour in the milk and cook, whisking constantly, until the sauce thickens. Add the grated cheese off the heat and stir until it melts. Season with the nutmeg and salt and pepper, to taste. Set aside.
Preheat the oven to 400 degrees.
Brush one side of 8 pieces of the bread with the Dijon mustard. Place 1 slice of ham over the mustard, cover with béchamel sauce, and add the second slice of ham and 1 slice of cheese. Place another piece of bread over the cheese and gently press on each sandwich.
Brush both sides of the sandwiches with the melted butter and line a baking sheet with parchment paper. Heat a nonstick pan over medium heat and sauté the sandwiches until golden brown on both sides.
Transfer the sandwiches to the baking sheet and cover the tops with béchamel sauce, saving any extra for another use. Top with the grated Jarlsberg cheese and place the baking sheet in the oven. Bake until the cheese turns golden, about 4-5 minutes — be careful not to let the cheese burn.
Trim the crusts from the sandwiches with a serrated knife and cut each into 4 squares. Serve immediately.