Chicken Cordon Bleu Casserole

Name: Chicken Cordon Bleu Casserole
Prep time: 15 min
Total time: 15 min
Cuisine: European
Ingredients: Cooking spray; 3 oz. prosciutto; 6 tbsp. unsalted butter; 6 tbsp. all-purpose flour; 1 c. chicken broth; 1 c. whole milk; 1 tbsp. Dijon mustard; 1 1/2 tsp. kosher salt; 1 tsp. freshly ground black pepper; 2 lb. boneless, skinless chicken breasts, cut into 1" pieces; 8 oz. cubed ham; 4 c. shredded Swiss cheese (about 1 lb.), divided; 1 panko bread crumbs; Chopped fresh parsley, for serving