In a 5-qt. slow cooker, combine beef, onions, mushrooms and garlic. In a small bowl, mix next 7 ingredients; pour over beef mixture. Cook, covered, on low until meat is tender, 6-8 hours., Skim fat from juices. In a small bowl, mix cornstarch and water until smooth; gradually stir into slow cooker. Cook, covered, on high until thickened, about 45 minutes. Serve with noodles; sprinkle with parsley., Freeze option: Omitting parsley, freeze cooled meat mixture, sauce and egg noodles in freezer containers. To use, partially thaw in refrigerator overnight. Microwave, covered, on high in microwave-safe dishes until heated through, stirring gently and adding water if necessary. Sprinkle with parsley.