Bitter melon (ku gua, 苦瓜, literally bitter cucumber) is one of the most distinctive and polarising ingredients in Chinese cooking — its intense, clean bitterness (from the compound momordicin) is considered a health food in Chinese medical tradition (believed to clear heat from the body and lower blood sugar). In Cantonese cooking, bitter melon is typically stir-fried with black beans and pork — the fermented black beans providing deep umami that complements the bitterness, and the pork fat providing richness that softens the edge of the bitter flavour.
Reducing the bitterness (optional): Many Chinese cooks salt the sliced bitter melon (after removing the seeds and pith) for 20-30 minutes, then rinse thoroughly. This draws out some of the bitter compound. Others prefer the full bitterness and skip this step. The technique: The bitter melon is cut into thin slices (3-5mm). The black beans (douchi) are rinsed and roughly mashed. Heat the wok. Fry the pork (thinly sliced pork belly or pork shoulder) until lightly browned. Add garlic, ginger, and the mashed douchi — fry briefly until fragrant. Add the bitter melon. Stir-fry at high heat 3-4 minutes — the bitter melon should soften but retain some crunch. Season with light soy, a small amount of oyster sauce, and sesame oil. The bitter melon will turn from bright green to a slightly duller, olive green during cooking.
Fuchsia Dunlop, Land of Fish and Rice (2016); Eileen Yin-Fei Lo, Mastering the Art of Chinese Cooking (2009)