This member of the cabbage family has a number of different names, including pak choi, bok choy, horse's ear, Chinese celery cabbage and white mustard cabbage. Its structure looks like a squatty celery stalk.
The texture of both leaves and stalks is crisp, and the flavor is somewhere between mild cabbage and spinach. If very young it can be eaten raw in salads, but is best when briefly cooked. Try it in a stir fry, steamed, or simmered in water - treat it pretty much as you would regular cabbage.