Easy Chicken Tetrazzini without margarine

1 tablespoon reduced-calorie margarine 1/2 cup scallion , chopped (about 5 scallions) 8 ounces button mushrooms , sliced 3 tablespoons all-purpose flour 1/4[...]

half box cooked spaghetti 2 cooked chicken breasts, shredded (or leftover rotisserie chicken) 1 (14 ounce) can chicken broth parmesan cheese (canned is fine)[...]

8 ounces vermicelli, broken in half 2 tablespoons butter or 2 tablespoons margarine 1 onion , small, diced 2 celery , large stalks, diced 2 garlic cloves ,[...]