Croque Monsieur

Name: Croque Monsieur
Ingredients: 2 tablespoons Butter ; unsalted; 3 tablespoons All purpose flour; 2 cups Milk ; hot; 1 teaspoon Kosher salt; 1/2 teaspoon Black Pepper ; freshly ground; 1 pinch Nutmeg; 12 ounces Gruyere cheese; 1/2 cups Parmesan Cheese ; grated; 16 slices White bread; 1/4 cup Dijon mustard; 8 ounces Ham ; virginia, sliced thin