Sze gwa goes by various names, such as angled loofah, ridged gourd and Chinese okra (it does resemble a large version of Western okra, aka lady fingers, although they're not related). It doesn't look the most enticing of vegetables - it's long, tapered (and sometimes curved) and the skin is (or should be) dull with a slightly rough texture.
Buy the smaller specimens of the vegetable, because with the large ones the numerous seeds are tough and the texture is spongy rather than smooth.
Sze gwa has a mild, slightly sweet flavour. If allowed to fully mature on the vine, it can be dried, then used as a loofah sponge.
Small, young sze gwa is easy to prepare - it just needs to be sliced - and the entire thing is edible. With larger ones, it's best to pare off the thick ridges, which can be tough, or even remove the skin. Some cooks also scrape out and discard the seeds.
The easiest way to prepare sze gwa is to steam it. Slice it lengthwise, cut into evenly sized pieces, then lay these cut-side up in a flat dish. Steam for about five minutes, then scatter spring onions on top and drizzle with a little light soy sauce before serving.
My favourite way to eat it is in soup. Soak dried shrimp in warm water for about 30 minutes. In another bowl, soak fen si (bean thread vermicelli) in hot water until pliable, then drain. Marinate sliced pork (or boneless dark meat chicken) with soy sauce, rice wine, white pepper, sugar, a pinch of salt and a little cornstarch. Put the dried shrimp (and the soaking liquid) in a saucepan, add some unsalted chicken broth and bring to the boil. Add the meat, fen si and some sze gwa that's been halved lengthwise and cut into pieces. Bring to a boil, then lower the heat and simmer until the meat is cooked and the vegetable tender. Add some minced spring onion, drizzle with a little sesame oil and sprinkle with white pepper before serving.