Bok choy, also known as Pak choi or Peking cabbage, forms a small but elongated head (not round like European cabbage) with plump white stalks and deep green leaves. A member of the brassica family, bok choy offers nutritional assets similar to those of other cabbages: It is rich in Vitamin C and contains significant amounts of nitrogen compounds known as indoles, as well as fiber--both of which appear to lower the risk of various forms of cancer. Bok choy is also a good source of folate (folic acid). And with its deep green leaves, bok choy has more beta-carotene than other cabbages, and it also supplies considerably more calcium. The stalks and leaves have quite different textures, so in culinary terms, it's like getting two vegetables for the price of one.
The most commonly seen bok choy in American markets has thick, chalk-white stalks and deep green, veined leaves. Asian markets offer several other varieties, some of which have green stalks. Tat soi is another variety; its leaves grow in a large, flat rosette.
Bok choy is available year-round. If you can't find it at your supermarket, look for it at an Asian market.
The stalks of bok choy should be thick and fleshy, but firm; the leaves should be crisp and green. Avoid bok choy with bruised or slimy spots.
Place unwashed heads of bok choy in a loosely closed plastic bag and refrigerate for no more than a day or two. Bok choy is more perishable than head cabbages.
Rinse under cold running water and shake dry. Small (baby) bok choy has a mild enough flavor to eat raw; the stalks resemble celery (although they are not "stringy" like celery), and the finely shredded leaves can go into salads. More mature specimens have a sharper flavor that is tamed with cooking: The stalks turn sweet and almost creamy, and the leaves taste something like Swiss chard.
Baby bok choy can be cooked whole by steaming or braising. When cooking more mature specimens, you'll want to cut the leaves from the stalks because the stalks will take longer to cook. Slice the stalks, and begin cooking them first. When the stalks begin to soften (about 2 minutes), add the shredded leaves and cook just until wilted.
Bok choy is a natural for stir-fries and can also be steamed. The shredded leaves are a refreshing last-minute addition to a simple soup or broth.