The Croque Monsieur is the most fancy pants grilled ham and cheese sandwich you will ever take a fork and knife to. This impressive version of the French bar snack has crisp, buttered bread; salty-sweet ham; and velvety mornay oozing out all over the place - and it is mind-blowing.
Instead of making them one at a time over the stove, I assembled several at a time on a baking sheet, layering in the cheese sauce and ham before topping them all with more sauce and cheese. They all go under the broiler together, and that was all that is needed to meld these over-the-top ingredients together, creating a bubbly-browned top in the process.
Sandwich Ingredients
(makes four sandwiches)
8 slices of bread
4 tablespoons unsalted butter, melted (I like Kerrygold)
12 ounces thinly sliced Black Forest deli ham
1/4 cup grated Parmesan cheese
4 ounces Gruyere cheese, shredded (about one cup)
Mornay Sauce Ingredients
2 tablespoons unsalted butter
2 tablespoons flour
1 cup whole milk
4 ounces Gruyere cheese, shredded (about one cup)
1/4 cup grated Parmesan cheese
1/2 tablespoon of whole grain mustard
1/2 teaspoon kosher salt
1/4 teaspoon pepper
Pinch of nutmeg
Sandwiches
We need to first toast all the bread. I prefer to do this in a toaster because it will toast evenly on both sides this way. Another way is to brush the bread on both sides with butter and then broil them on a sheet pan, and flip and toast the second side. If you go this route, I found it helpful to spray the sheet pan with vegetable oil spray first. Once the bread is golden brown on both sides we can begin building the gourmet sandwiches.
Mornay Sauce
Melt butter in a medium saucepan over medium heat until foamy. Add the flour and cook for one minute. Slowly whisk in milk and bring to a boil. Once boiling, remove from heat and add the grated Gruyere and Parmesan cheese along with mustard, salt, pepper, and nutmeg. Stir until smooth.
Bake and serve
Spread 1 tablespoon of Mornay sauce on each slice of toast. Top four slices with folded ham and top them each with the remaining four slices, sauce side down. The order from bottom to top is toast, mornay, ham, mornay, toast.
Just when you think this could not be more unhealthy, we are going to cover the top of each sandwich with 2 tablespoons of mornay, making sure to completely cover the sides because exposed edges will burn under the broiler. Sprinkle each sandwich with Parmesan, followed by Gruyere.
Bake at 375 for about 5 minutes, until cheese on top of the sandwich is melted. Turn on the broiler and broil until the cheese bubbles across tops of sandwiches and edges are spotty brown, about 5 more minutes.