Ingredients:

  • 30g unsalted butter
  • 30g all-purpose flour
  • 300ml whole milk, room temperature
  • 1g freshly grated nutmeg
  • Salt and black pepper to taste
  • 250g Gruyère cheese, freshly grated (divided)
  • 8 slices thick-cut sourdough or brioche bread
  • 60g unsalted butter, softened
  • 200g high-quality jambon de Paris or honey-roasted deli ham
  • 20g Dijon mustard

Instructions:

  1. Prepare the Béchamel Sauce: In a small saucepan over medium heat, melt 30g butter. Whisk in flour and cook for 1–2 minutes to create a light roux. Gradually whisk in the milk until smooth. Simmer until thickened, then remove from heat and stir in 50g of Gruyère, nutmeg, salt, and pepper.
  2. Toast the Bread: Preheat oven to 200°C (400°F). Butter both sides of the 8 bread slices using 60g of softened butter. Place on a baking sheet and toast for 3–5 minutes per side until lightly golden.
  3. Assemble the Sandwich: Lay 4 slices of toasted bread on the baking sheet. Spread a thin layer of Dijon mustard on each. Top with ham and a portion of the grated Gruyère. Place the remaining 4 bread slices on top.
  4. Apply Topping: Spread a thick layer of the prepared Béchamel sauce over the top of each closed sandwich, ensuring it reaches the edges. Sprinkle the remaining Gruyère cheese over the sauce.
  5. Bake and Broil: Bake at 200°C (400°F) for 5 minutes. Switch to the broiler setting for 2–3 minutes until the cheese is bubbling and browned. Serve immediately.