- 4 tablespoons butter
- 3 tablespoons flour
- 2 cups whole milk
- 1/4 teaspoon salt
- 1/8 teaspoon pepper
- 1/8 teaspoon nutmeg
- 1 cup grated Gruyère cheese
- 1/4 cup grated Parmesan cheese, plus more for garnish
- 8 thick-cut slices of French bread
- 4 teaspoons Dijon mustard
- 4 eggs
- 16 slices of prosciutto
- 1 tablespoon finely diced chives
1. Heat a saucepan over medium and melt 3 tablespoons of butter. When the butter has melted, add the flour and stir together. Cook, while continuing to stir, for 1 minute. Add milk and continue stirring until your roux has incorporated and the milk thickens, about 5 minutes. Remove from the heat.
2. Add your salt, pepper, nutmeg and cheese, and stir to combine. Stir the sauce every minute or so, until the cheese has melted.
3. Preheat your broiler.
4. Lay 4 pieces of bread on a baking sheet. Spread 1 teaspoon of Dijon on each piece. Top with 2 pieces of prosciutto and 1 tablespoon of sauce. Cover with a second piece of bread and coat the top with 2-3 tablespoons more sauce.
5. Cook under a broiler until the sauce is melted, golden and bubbling, 2- 3 minutes. Turn off the broiler and transfer sandwiches to the lower rack of the oven to keep warm.
6. While the sandwiches are cooking, heat a remaining tablespoon of butter in a pan over medium. Crack eggs and fry until the whites are set but the yolks are runny.
7. Top the sandwiches with an egg and 2 pieces of prosciutto. Grate some Parmesan cheese and sprinkle on chives.