In this simple, speedy stir-fry garlic and chili complement the bok choy without muddling its fresh, subtly sweet cabbagey notes. Shaoxing wine has a rich, slightly nutty flavor. It’s worth searching it out in well-stocked supermarkets or at the Asian grocery store, but if it is not available, dry sherry is a fine substitute. So the bok choy cooks in the right amount of time, look for heads 4 to 5 inches long and 2 to 3 inches in diameter, with bright white stems and deep green leaves. The layers can trap sand at the base; cleaning is easiest after the heads are halved. Plunge them into cold water and swish them about, then drain well and dry thoroughly, as excess water will cause wateriness in the finished dish.