A Croque Madame is a next-level grilled ham (or turkey) and cheese sandwich with Mornay sauce that’s topped with fried egg. Find out how easy this French bistro classic is to make at home, including a homemade Mornay sauce that whips up in 5 minutes!
Add the butter to a small saucepan over medium heat. Once the butter is mostly melted, whisk in the flour. Cook for 30 seconds to 1 minute, whisking frequently. Whisk in the milk, and cook until thickened, about 30 seconds. Whisk in the salt, black pepper, and nutmeg. Turn the heat down to low and whisk in the cheese until well-combined (it will be very thick). Remove from the heat.
To Assemble the Sandwiches:
Butter 1 side of each piece of bread with 1 teaspoon of butter. Lay the bread (buttered side down) on a cutting board.
Spread 3 tablespoons of Mornay sauce on each of two slices of bread. Top each with 2 ounces of sliced turkey, and about 3 tablespoons of shredded cheese. Spread the Dijon on the remaining two slices of bread. Flip the bread with the Dijon over onto the bread topped with cheese.
Place the sandwiches in a medium skillet and cook over medium-low heat until golden brown on both sides (about 2 to 3 minutes per side).
Preheat the broiler, line a baking sheet with aluminum foil, and transfer the sandwiches to the prepared baking sheet.
Divide the remaining Mornay sauce between the tops of both sandwiches, making sure to spread the sauce to the edge of bread so that the whole top of the sandwich is covered (you can add a little more shredded Gruyère on top if you have it). Broil a few minutes until the Mornay is bubbling and starting to turn golden in spots.
Turn off the broiler and transfer the sandwiches to the oven to stay warm while you fry the eggs.
To Serve:
Transfer the sandwiches to serving plates and top each with a fried egg and chives.
Notes
Recipe Yield and Serving Size: This recipe makes 2 large sandwiches, and honestly, each sandwich is enough for 2 servings (especially if you serve each half topped with a fried egg).
Cheese: 1 ½ ounces of shredded Gruyère is about 6 tablespoons of cheese.
Make Ahead: You can make these sandwiches up to 3 days ahead of time, and wait to top them with fried eggs until right before serving. To reheat the sandwiches, put them on a baking tray, and heat them in a 350F oven until warm throughout, about 5 to 8 minutes.