I'm usually in the kitchen most of the day making some kind of dish for my family, neighbors or the local fire department to pass around and try. My husband is a firefighter in our town, and this casserole is a favorite there.
Cook spaghetti according to package directions; drain.
In a large bowl, combine the soups, sour cream, milk, 2 tablespoons butter and seasonings. Add the cheeses, celery, onion and mushrooms. Stir in the chicken and spaghetti.
Transfer to a greased 3-quart dish (dish will be full). Combine the cornflakes and remaining butter; sprinkle over the top.
Bake, uncovered, at 350 degrees for 45–50 minutes or until bubbly.