Heat peanut oil in a wok or 12-inch heavy skillet over high heat until just beginning to smoke then stir-fry garlic and ginger with salt until fragrant, about 30 seconds. Add cabbage and cook, tossing, until just beginning to wilt, about 2 minutes, then stir in chestnuts and sugar. Reduce heat to moderate and cook covered, 3 minutes, then stir in soy sauce and sesame oil. Serve immediately.
