One day, my friend Frank Newbold and I found ourselves on the way to the Louvre at lunchtime. We passed Café Ruc, which is one of the Costes brothers’ restaurants, and spotted two seats outside under the awning. They serve traditional French food, but with a modern twist. This was inspired by the delicious croques monsieurs we ate there. These sandwiches are on the small side, so serve one or two per person, depending on appetites.

Steps

1. Preheat the oven to 400 degrees.
2. Melt the butter over low heat in a small saucepan and add the flour all at once, stirring with a wooden spoon for 2 minutes. Slowly pour the hot milk into the butter-flour mixture and cook, whisking constantly, until the sauce is thickened. Off the heat, add the salt, pepper, nutmeg, ½ cup grated Gruyère, and the Parmesan. Set aside.
3. To toast the bread, place the slices on two baking sheets and bake for 5 minutes. Turn each slice and bake for another 2 minutes, until toasted.
4. Lightly brush half the toasted breads with mustard, add a slice of ham to each, and sprinkle with half the remaining Gruyère. Top with another piece of toasted bread. Slather the tops with the cheese sauce, sprinkle with the remaining Gruyère, and bake the 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.