Choi Sum with Oyster Sauce

Not for nothing is this green flowering cabbage called choi sum, which means the heart of the vegetable, for it is only the stalk in the centre that is tender and delicious to eat while the outer stalks, belying their green looks, are stringy and tough. You can expect to lose one third to one half of the weight of choi sum in the cooking. Wasteful as they may seem, the Cantonese adore choi sum for their delicate taste; more often than not, they simply blanch them and lace them with oyster s