Cut the stem ends off the bok choy. Then cut the stalks into 1-inch sections.
Heat the wok, then add the peanut oil and heat over a medium flame until very hot but not smoking.
For a generic Stir-fry of bok choy, toss in the ginger and Stir-fry for a few seconds. Then stir in the bok choy and garlic. Continue Stir-frying for 2 minutes, or until the bok choy has lost its turgor but the leaves are still bright green. Season with salt, sugar, and sesame oil.
For a Sichuanese quick-fry (qiang) of bok choy, substitute the chiles and Sichuan peppercorns for the ginger and garlic. Add both ingredients as soon as the oil is hot and Stir-fry very briefly. Then add the bok choy sections and proceed as above. Fuchsia Dunlop recommends adding a splash of black vinegar just before serving “for a fabulous extra kick of flavor.”