Tuna Noodle Casserole

Name: Tuna Noodle Casserole
Ingredients: Kosher salt; 6 ounces wide egg noodles; 2 tablespoons unsalted butter; 6 scallions (white parts sliced, green parts finely chopped); 3 stalks celery, thinly sliced, plus 2 tablespoons chopped leaves; One 12-ounce can fat-free evaporated milk; Freshly ground pepper; 1 cup frozen peas and carrots; 1 tablespoon Dijon mustard; 1/2 cup light sour cream; 3/4 cup shredded low-fat Monterey jack cheese (about 3 ounces); One 5-ounce can water-packed tuna, drained and flaked; 1/4 cup panko breadcrumbs