- 2 tablespoons butter, plus additional for bread
- 2 tablespoons all-purpose flour
- 1 cup milk
- Pinch of nutmeg
- Salt and pepper, to taste
- 4 slices sandwich bread
- 1 tablespoon Dijon mustard
- 4 slices cooked ham
- 2 slices Gruyère cheese
- 1/4 cup grated Gruyère cheese
Melt butter in a saucepan over medium heat. Stir in flour to create a thick paste. Slowly whisk milk in to the flour mixture in a steady stream. Cook for 5 minutes to thicken sauce, stirring often. Stir in a pinch of nutmeg and season to taste with salt and pepper. Keep warm.
Make two sandwiches with bread slices, mustard, ham and sliced cheese. Lightly spread both outer sides of bread with butter. Heat a large oven-proof skillet over medium-low heat. Place sandwiches in the warm skillet and cook on one side until golden brown and cheese begins to melt, 2 to 4 minutes. Flip sandwich over and cook until golden brown and cheese is melted, 2 to 4 additional minutes.
Top sandwiches with the sauce and grated cheese. Broil until golden brown and bubbling, 5 to 7 minutes. Remove from the oven and let sit 2 to 3 minutes before cutting.
To prepare a Croque Madame, prepare recipe as above and top each sandwich with a fried egg.