Rachel Khoo makes croque madame or what we call a toasted cheese and ham sandwich on The Little Paris Kitchen.

The ingredients for the cheese sauce are: 1 tablespoon (1/2 ounce) unsalted butter, 1 tablespoon all-purpose flour, 3/4 cup plus 1 tablespoon lukewarm milk, preferably whole, plus more as needed, 1/2 teaspoon Dijon mustard, 1/2 teaspoon freshly grated nutmeg, 1/4 cup grated Gruyère or mature Comté cheese (or a strong hard cheese like Parmesan or mature Cheddar), plus more for sprinkling and Salt and freshly ground black pepper to taste.

For the muffins: 6 slices white bread, crusts removed, 3 tablespoons (1 1/2 ounces) unsalted butter, melted, plus more for the tin, 2 1/2 ounces ham, cut into cubes or thin strips and 6 small eggs.