Separate, wash & dry cabbage leaves. Stack them up and cut them crosswise into 1" wide pieces. Finely mince or grind Szechwan peppercorns. Crush rock sugar with cleaver handle; mix with soy sauce; reserve. Stir-frying: Heat wok to moderate; add oil. Wait 30 seconds. Stir-fry whole chilies until they just blacken; quickly add peppercorns. When they exude pungent odor, push up side of wok and raise heat to high. Add salt & cabbage all at once. Keep tossing cabbage until it is wilted & soft. This takes several minutes. There should be about 2 T of water in wok when cabbage is wilted. Add sugar & soy mixture. When sugar has melted, toss with cabbage, then sprinkle vinegar over all. Keep tossing on high heat for another 20 seconds. Add sesame oil; toss briefly; remove to serving dish. If serving this dish cold, wait until it has cooled, then cover & refrigerate.