A popular vegetable frequently found in Hong Kong markets, this is a long, thin, cylindrical squash, tapering at one end with deep narrow ridges. Choose firm, unblemished dark-green ones. Peel the ridges. If the squash are young, you can leave some of the green; if they are older, it is best to peel all the skin. The inside flesh turns soft and tender as it cooks, like a cross between a cucumber and a courgette. Absorbent, it readily picks up flavours of the sauce or food it is cooked with.