Put a large chunk (I use about a 1/2 of a stick of margarine) in skillet & melt. Add chopped onion & bell pepper & saute' until tender. Add the cream of chicken soup, small can mushrooms (I don't like them so I leave these out), small jar diced pimento, the cans of chicken breast WITH juices, flour & small can evaporated milk. You add enough flour to thicken and simmer all in skillet. Meanwhile cook your spaghetti till tender in another pan. When the chicken mixture has thickened a bit (but not too thick simmer for only around 10 or 15 minutes)..get ready to layer in 9 X 13 casserole dish. Spray dish with Pam or similar spray oil..then layer drained cooked spaghetti, then chicken mixture, then cheese. Continue layering until you've filled the dish & top with cheese.
Bake at 350 degrees for 30-40 minutes until cheese is melted. Serve with green salad & it's a meal!