Ingredients:

  • 2 tablespoons (28g) unsalted butter, plus more for spreading
  • 2 tablespoons (15g) all-purpose flour, plus more for dusting
  • 1 ½ cups (360ml) whole milk
  • ¼ teaspoon ground nutmeg
  • Salt and freshly ground black pepper to taste
  • 4 slices white bread (such as pain de mie or brioche), about ½ inch thick
  • 4 tablespoons Dijon mustard (approx. 60ml)
  • 4 ounces (115g) thinly sliced cooked ham, preferably Parisian-style ham (jambon de Paris)
  • 4 ounces (115g) Gruyère cheese, grated
  • (Optional) 2 tablespoons grated Parmesan cheese, for topping

Instructions:

  1. Make the Béchamel Sauce: Melt butter in a saucepan. Whisk in flour and cook for 1 minute (a roux!). Gradually whisk in milk until smooth. Bring to a simmer, whisking constantly. Reduce heat and simmer for 5 minutes, or until thickened. Stir in nutmeg, salt, and pepper. Remove from heat.
  2. Assemble the Sandwiches: Lightly butter one side of each bread slice. Spread the unbuttered side of each slice with Dijon mustard.
  3. Layer the Ham & Cheese: On two slices of bread, layer half the Gruyère cheese, the ham, and then the remaining Gruyère cheese. Top with the other slices of bread, mustard-side down.
  4. Top with Béchamel: Spread the top of each sandwich with béchamel sauce. Sprinkle with Parmesan cheese (if using).
  5. Bake or Broil: Bake in a preheated oven at 375°F (190°C) for 10-12 minutes, or until golden brown and bubbly. Alternatively, broil for 2-3 minutes, watching carefully to prevent burning.