Saute chicken in oil until browned. Remove and set aside. Add onions to pan, saute for 5 minutes. Add tomatoes and bell pepper. Saute for 10 minutes. Add thyme, bay leaf, salt, and cayenne. Mix peanut butter with chicken stock until smooth. Place chicken in baking dish, pour over tomato mixture, stock mixture and green beans. Bake at 350 degrees for 1 hour. Serve over rice.