Remove any blemished outside stalks from the greens. Put the spinach to one side so that you can add it to the wok or pan at the last minute, as it cooks very quickly. Prepare the rest of the Chinese greens; i normally cut the Chinese broccoli into strips and the bok choy into quarters. Plunge the greens into boiling water for about 1 1/2 minutes until just tender, and drain well.
Put the oil and the ginger into a very large, hot wok or other suitable pan and cook for about 30 seconds. Add the scallions and the rest of the ingredients apart from the seasoning. Stir, then add the spinach and toss so that everything is coated in sauce. The vegetables will sizzle and stir-fry. The oyster and soy sauce will reduce, just coating the greens. At this point season to taste. Stir-fry for a further minute and serve immediately.