Sliced beef is stir-fried with bitter melon in a black bean sauce that tames the vegetable's sharp edge. This healthy, high protein dish is prized in Chinese cuisine for supporting lower cholesterol and diabetic-friendly eating.
Slice the beef thinly across the grain, and toss with 1 tbsp soy sauce, Shaoxing wine, white pepper, 0.5 tsp cornstarch, and 0.5 tbsp oil. Marinate for at least 15 minutes.
Cut the bitter melon lengthwise, remove seeds, then slice into thin crescents. Rub with 0.5 tsp salt (not listed) and let sit 10 minutes; rinse well and drain.
Mix black beans, remaining soy sauce, oyster sauce, sugar, and 0.5 tsp cornstarch with 2 tbsp water to make the stir-fry sauce.
Heat 1.5 tbsp oil in a wok on high until just smoking. Add beef in a single layer, sear for 30 seconds without moving, then stir-fry another 30 seconds until nearly cooked. Remove beef and set aside.
In the same wok, add garlic and onions, stir-fry 30 seconds, add bitter melon and a splash of water. Stir-fry on medium-high until melon brightens and softens slightly, 2–3 minutes.
Return beef to the wok, pour in sauce, and toss everything together on high heat. Stir-fry just until sauce thickens and beef is coated (30–45 seconds). Serve hot immediately.