Preheat oven to 350F. Melt butter; brown onions, celery and pepper until wilted. Add chicken broth, mushrooms, tomatoes and sauce. Simmer over low heat. Cut chicken into bite sized pieces and cook until browned through. Add chicken to sauce. Stir well. Boil spaghetti, then drain. Place spaghetti in casserole dishes. Cover the spaghetti with the sauce. Slice the Velveeta cheese and cover. You should have three layers. Bake at 350F until cheese melts and bubbles.
Cajun Country -- New Iberia, Louisiana