Melt butter and brown chicken in a heavy 11" skillet.
Remove chicken; lightly brown onion, green pepper and garlic.
Place chicken back in skillet, spooning onion and green pepper over.
Stir together in a medium bowl undrained tomatoes, tomato sauce w/mushrooms, salt, pepper, thyme, bay leaves and cayenne pepper. Pour over chicken. Bring to a boil. Reduce heat and simmer uncovered 30-40 minutes or until chicken is fork tender.
Remove bay leaves. Transfer chicken to warm platter. skim off any extra fat from sauce, spoon some sauce over chicken. Thicken remaining sauce slightly and stir into pre-cooked spaghetti, adding additional 8 oz can of tomato sauce w/mushrooms in necessary to make enough liquid.