Croque Monsieur

Ingredients

• Dijon mustard
• Pinch nutmeg
• 2 tablespoons unsalted butter
• 1/2 cup freshly grated Parmesan
• 8 ounces baked Virginia ham, sliced but not paper thin
• 16 slices white sandwich bread, crusts removed
• 3 tablespoons all-purpose flour
• 1 teaspoon kosher salt
• 2 cups hot milk
• 1/2 teaspoon freshly ground black pepper
• 12 ounces Gruyere, grated