Croque Monsieur, the French hot sandwich, is thought to have originated in bistros in the early 1900s in France (see here). Literally translated Croque Monsieur means Mister Crunch.
Many versions of this sandwich exist. Mine differs in a couple of ways. First, I use only one slice of bread, making it an open-faced sandwich. I believe one thicker slice of bread is all you need to support the sandwich, plus it allows the filling ingredients to take the starring role. In addition, it cuts down on the cooking time, as there’s no need to bake the Croque Monsieur before browning under the broiler.
It’s essential to use a high quality, white sandwich bread with a soft crust, such as pain de mie or Japanese milk bread. Most supermarket breads tend to be too spongy and sweet to serve the purpose (if you use one, choose a hearty loaf). Second, I toast the bread, buttered in a skillet, rather than a sheet pan in the oven. I believe it gives the bread more body and a better flavor.
The traditional cheese for this is Gruyere. Some like to mix in some Parmesan as well. I find this unnecessary. You should use nicely smoked ham that is sliced a little on the thicker side. I use Black Forest ham.
The Bechamel
Heat the milk and a half teaspoon of salt in a small saucepan until it begins to simmer.
Melt 3 tablespoons of butter in a heavy sauce pan. When the butter is melted, whisk in the flour until the mixture is smooth. This is called a roux.
Add flour to melted butter.
Cook for a minute or two, then whisk in all the hot milk at once. Bring to a boil and continue to beat until the mixture is very thick and smooth.
Thick bechamel.
Add the bay leaf (this add extra flavor), the freshly ground nutmeg, and the black pepper, and continue to simmer on very low heat for 5-10 minutes, stirring frequently.
The Mornay Sauce
Add 3⁄4 cup of the grated Gruyere to the sauce, stirring until it melts. This transforms the bechamel into a Mornay sauce.
Add cheese for a Mornay sauce.
Remove from the heat and set aside. The sauce can be made a day ahead and refrigerated, with plastic pressed against the sauce to prevent on skin from forming. Before using, warm the Mornay so that it spreads more easily.
Croque Monsieur Assembly
Cut the bread into four 3⁄4-inch-thick slices. Spread both sides of the bread with the softened butter. Heat in a skillet until the bread is nicely toasted. Turn the slices and toast on the other side.
Toast buttered bread in a skillet.
Remove the bread to a broiler pan.
In the same skillet, heat the ham slices on both sides, just until speckles of brown appear.
Lightly fry the ham.
This is a totally optional step, but I believe it enhances the flavor of the ham.
Remove the bay leaf from the Mornay sauce. Spread a thin layer of sauce on the bread slices.
Spread Mornay on the bread.
Arrange the ham slices on top of the Mornay.
Arrange the ham slices.
Spread a thick layer of Mornay sauce to cover the ham on each slice.
Spread a thick layer of Mornay over the ham.
Lightly press the remainder of the grated cheese into the Mornay sauce.
Top the Mornay with cheese.
Place under a broiler for several minutes, until the sauce is bubbly and begins to develop golden brown spots. Check the broiler frequently to be sure that the croques are not burning.
Place the Croque under the broiler.
Some people like to top the completed Croque Monsieur with a sunny-side-up fried egg. This turns the sandwich into a Croque Madame.
Makes four sandwiches. Serve with cornichons, which help cut through the richness of the sandwich.
Serve with cornichons.
