Debone chicken and remove skin. In large skillet heat butter and oil. Saute' chicken on both sides until brown. Remove from pan. In same skillet saute' onions and celery about 5 minutes. Blend in flour; slowly add water with chicken bouillon dissolved in it. Add can of whole tomatoes and stir till mixture comes to a boil. Season with salt + pepper. Add chicken, sherry and parsley. Cover, simmer until tender, about 30 minutes.