Croqué Monsieur

For the sauce:
In a medium saucepan, heat the butter over medium-low heat until melted. Add the flour and stir until smooth. Over medium heat, cook until the mixture turns a light, golden sandy color, about 6 to 7 minutes.

Meanwhile, heat the milk in a separate pan until just about to boil. Once your butter mixture turns a golden sandy color, add the hot milk to the butter mixture 1 cup at a time, whisking continuously until very smooth. Bring to a boil. Cook 10 minutes, stirring constantly, then remove from heat. Season with salt and nutmeg, and set aside until ready to use.

For the assembly:
Spread each slice of bread with mustard, then divide ham, 1 cup cheese, and 1/2 cup sauce over mustard-topped slices and top with remaining pieces of bread. Top with remaining sauce and cheese. Cover the sandwiches, weigh them down and refrigerate for 1 hour.

An hour later…..
Heat oven to 475 degrees (F). Bake until cheese is golden brown and bubbling, about 8 to 10 minutes.