Tuna Noodle Casserole

Name: Tuna Noodle Casserole
Ingredients: 4 stalks celery, diced; 1 tablespoon butter; 0.5 cups milk; 0.5 tablespoons cornstarch, mixed in a small bowl with 1/2 tablespoon water; 4 ounces cheddar cheese, shredded; 4 ounces elbow macaroni, cooked al dente according to package; 4 ounces (one small can) of tuna, drained well; 0.25 cups french-fried onions (optional); Salt, to taste; Pepper, to taste