Tianjin Bok Choy

This is a vegetable of many names. Often called Tianjin cabbage, Tientsin bok choy (the old spelling of its home city), or celery cabbage, it is also known familiarly as napa cabbage. There are two varieties of this very white, green-tinged vegetable—one with a long stalk, and the second rounder and heavier. The latter is the one most often called by its native city name; it is also the sweeter of the two, and my preference. At its best in late spring and summer, it should be kept in a plastic bag in the refrigerator for no more than 3 or 4 days, after which small, black marks begin to appear on the stalks. I suggest eating it as soon as possible after purchase. Heads range from 3 to 8 pounds, and some grocers will cut the larger heads to accommodate shoppers.