How do you cook bok choy? What are the differences among its varieties?
There are dozens of Chinese cabbages, but only two—Napa and bok choy—are widely available in American supermarkets. Napa cabbage has frilly, pale green leaves. Although it can be cooked, we find this rather bland cabbage is best shredded and used raw in spicy Asian-style slaws. Bok choy is another story entirely. Although a member of the cabbage family, this vegetable resembles leafy greens, especially chard. Its crisp, ivory stalks and crinkly, dark green leaves are easy to recognize.
Unlike so many leafy greens, bok choy doesn’t shrink down to nothing when cooked. The stalks are crisp and fleshy—like celery, but not stringy. In fact, when cooked fully they become creamy, with an almost meatlike texture and an underlying sweetness. In contrast, the leaves become tender and soft, having an earthy, robust flavor similar to that of chard or even spinach.
But for all of its virtues, there are some issues to look at when cooking this vegetable, especially for American cooks who are not familiar with its characteristics. If not prepared properly, bok choy can turn mushy and pallid, losing its considerable appeal. Our goal was simple: to devise a cooking method that would produce perfectly cooked (and seasoned) bok choy—both the leaves and stems.
We combed through several dozen cook¬books looking for recipes. A few non-Chinese sources suggested cooking the stalks and greens together. We were skeptical, since all of the Chinese sources we consulted called for separating the stalks and leaves so that the stalks could be cooked longer. Nonetheless, we went ahead and tried stir-frying roughly chopped bok choy stalks and greens together. Rather predictably, we were disappointed. If we cooked the bok choy briefly, the greens were fine but the stalks were much too crunchy. Increasing the stir-fry time softened the stalks, but the leaves turned limp and unappealing.
We now knew that we were going to have to separate the white stalks and green leaves before cooking. We started by trimming and discarding the bottom inch of the stalks, which is often tough and blemished. This also served to separate the leaves so that each one could be washed and patted dry individually.
With our bok choy prepped, it was time to start testing cooking methods. Most methods we uncovered in our research made some effort to deal with the fact that the stalks require a longer cooking time than the greens. After a few tests, we quickly dismissed blanching or steaming the stalks. Steaming was better than blanching (which washed away too much flavor), but both methods made the bok choy watery.
We had better luck stir-frying bok choy in a large nonstick skillet—the test kitchen’s preferred ves¬sel for stir-frying because of its wide, flat surface area. Throwing the sliced stalks into the pan first gave them the necessary head start. After stir-frying for five minutes, the stalks were crisp-tender and beginning to brown. We could then add the leaves and continue stir-frying for another minute or so until the leaves wilted.
Some sources suggested covering the pan after adding the leaves. But because we had also decided to add a sauce to the pan at the same time, covering the stir-fry made it a bit soupy; the sauce couldn’t evaporate and thicken. We decided it was better just to leave the cover off for the entire cooking time.
This stir-fry method has plenty of advantages. It’s simple, and the seasonings can be changed endlessly. The stalks, however, were still crisp-tender (increasing the stir-frying time didn’t seem to help much) and not as creamy as some of the bok choy dishes we’ve eaten in Chinese restaurants. We liked stir-fried bok choy, but we wondered if there was another option.
Several recipes we consulted suggested braising bok choy in a covered pan with some liquid, as you might do with kale or another tough green. We first stir-fried the stalks to give them color (and flavor from the browning), then added the greens and some stock and let the bok choy simmer away. After 10 minutes the stalks were soft but not mushy. Their texture was creamy and deli¬cious. The leaves were completely tender. Best of all, the flavor of the bok choy seemed more robust and earthy.
Both stir-frying and braising have their advan¬tages. Stir-frying results in a fairly dry dish, making bok choy a good partner on most dinner plates. Braising, which is not much more work than stir-frying, makes bok choy very moist and soft, an ideal partner for lean meat, fish, or chicken.
Although most American supermarkets carry only one kind of bok choy—the green-leaved, white-stalked variety—in Asian markets you might see three or four different vegetables all labeled “bok choy.”
In addition to the varietal differ¬ences, bok choy also comes in various sizes, from diminutive baby bok choy that weigh just four ounces to mammoth heads that weigh more than two pounds. Any variety of bok choy (with either white or green stems) picked at an early age can be called baby bok choy. Most heads weigh just three or four ounces and will fit in your hand. Because of their small size, the stalks are fairly tender, so there’s no need to cook them separately. Baby bok choy are best halved and seared.
This type of bok choy has jade-colored stalks that are slightly wider than the ivory stalks on regular bok choy and are shaped like Chinese soup spoons. Shanghai bok choy can be handled like regular bok choy.
This variety has small yellow flowers sprouting from the center of its dark green leaves. As with broccoli rabe, the flowers are edible. To keep the flowers bright, slice and cook them with the leaves and stir-fry rather than braise.
What you’re likely to find in the supermarket are medium or large heads of regular bok choy. In general, heads between 1 1/2 and 1 3/4 pounds are your best bet—one head yields four side-dish servings, but the stalks are still thin enough to cook up tender. In testing, we found that the stalks on larger heads (weighing two pounds or more) can be spongy and woody in the center. In terms of appearance, make sure the leaves are bright green and crisp. Leaves that are wilted or yellow are a sign of aging. The stalks should be bright white. If the stalks are covered with tiny brown spots, the bok choy is past its prime. Once you get bok choy home, it should be stored like other leafy greens—in a loosely sealed plastic bag in the refrigerator for up to two or three days. Don’t wash bok choy until you are ready to cook it. We found that prewashing accelerated the decay process.