Croque Madame

5 tablespoons unsalted butter

3 tablespoons all-purpose flour

2 cups whole milk

Salt and pepper

1/8 teaspoon nutmeg

1 1/3 cups grated gruyere cheese, about 3 ½ ounces

8 slices firm white sandwich bread (sourdough is really good for this)

4 teaspoons Dijon mustard

½ lb deli sliced ham

4 large eggs

Melt 3 tablespoons butter and a medium saucepan over moderate heat. Whisk in flour and cook, whisking, 3 minutes. Gradually whisk in milk and then bring to a boil, whisking constantly. Reduce heat and simmer, stirring occasionally, for 5 minutes. Whisk in salt and pepper to taste, nutmeg, and 1/3 cup cheese until well incorporated. Remove from heat and set aside.

Spread 1 ½ tablespoons of sauce evenly over each of 4 slices of bread, then sprinkle with remaining cheese, ¼ cup per slice. Spread 1 teaspoon mustard on each of the remaining bread slices then top evenly with ham. Invert ham covered slices onto cheese topped slices.

Spray a baking sheet with cooking spray.

In a large nonstick skillet, melt 1 tablespoon of butter over moderate heat. Toast sandwiches until golden on each side, about 4 minutes total. Remove from heat and transfer the sandwiches to the prepared baking pan.

Preheat broiler.

Top each sandwich with 1/3 cup sauce and spread evenly. Broil sandwiches until sauce is bubbly and golden in spots, about 3-4 minutes. Turn off broiler and keep sandwiches warm.

Heat remaining tablespoon of butter in nonstick skillet over moderate heat. Crack eggs into skillet and season with salt and pepper. Fry until whites are set and yolks are still runny, about 4 minutes. Top each sandwich with a fried egg and serve.