A type of Chinese vegetable of the mustard family. It has dark green leaves and white celery-like stalks that have a mild, slightly peppery flavor. Both the greens and the stalks are popular in salads and the stalks are often used in stir-fry recipes. Also known as bok choy, pak choi, choi sum, Chinese white cabbage, Chinese flowering cabbage, Peking cabbage, celery cabbage, and white mustard cabbage. Pak Choy is available throughout the year. When selecting, look for a firm compact head with fresh leaves. The cabbage should be used when fresh if possible because it does not store well. If it is necessary to store, keep it in the vegetable drawer of the refrigerator, wrapped in plastic, and it should stay fresh for 4 to 5 days.