- 1½ tablespoons unsalted butter
- 1½ tablespoons all-purpose flour
- 1 cup whole milk
- ¼ teaspoon kosher salt
- Pinch freshly grated nutmeg
- 2 tablespoons unsalted butter, softened
- 4 slices hearty white sandwich bread, country white bread or pain de mie
- Dijon mustard to taste
- 4 thin slices ham
- 2 thin slices Gruyere cheese
- Make the béchamel sauce:
Melt butter in a small saucepan over medium heat. Add flour and cook, whisking constantly, until raw flour scent has cooked off, 1-2 minutes. Slowly pour in milk, whisking constantly and thoroughly around edges of pan. Continue whisking and bring sauce to a simmer, then reduce heat to low and cook until sauce is thick enough to coat the back of a spoon, about 3 minutes. Season sauce with salt and nutmeg. Reduce heat as low as possible and keep warm while preparing sandwiches.
- Butter one side of each slice of bread and place buttered side down on a clean cutting board.
- Spread Dijon mustard on two of the slices. Arrange 2 slices of ham and 1 slice of Gruyere on top of the Dijon. Spread 2 tablespoons béchamel sauce on the other two slices of bread and close the sandwiches.
- Select AIRFRY/400°F/SUPER CONVECTION/5 minutes and press START to preheat oven.
- Place sandwiches on airfry rack and cook for 5 minutes. Remove airfry rack from oven and spread 2 tablespoons béchamel sauce over the top of each sandwich. Return airfry rack to oven and cook for an additional 2 minutes, until béchamel is bubbly and golden brown. Serve immediately.