Turkey Noodle Casserole

Name: Turkey Noodle Casserole
Ingredients: Salt; 1/4 cup unsalted butter; 2 cups sliced shallots or thinly sliced onions; 2 cups diced celery; 1/4 cup all-purpose flour; 12 ounces egg noodles; 1/3 cup dry vermouth or dry white wine; 1 1/2 cups milk; 1/4 cup cream or sour cream; 2 cups chicken or turkey stock; 2 teaspoons dry tarragon; 6 ounces grated Gruyere cheese; 2 tablespoons whole-grain mustard; 3 cups coarsely chopped cooked turkey; 1/2 teaspoon freshly ground black pepper; 2 tablespoons lemon juice; 1/2 cup panko breadcrumbs; 1 tablespoon melted butter; Freshly chopped parsley, for garnish, optional