From YouTube Happy Wok
Slice beef flank steak against the grain
Marinate beef with light soy sauce, rice wine, baking soda, and corn starch
Add oil to marinated meat and let sit
Prepare bitter gourd by slicing
Heat wok and stir-fry bitter gourd until tender
Remove bitter gourd from wok
Add oil to wok and stir-fry marinated beef until cooked
Add minced ginger, garlic, and fermented black beans
Return bitter gourd to wok
Mix sauce ingredients (beef broth, oyster sauce, light soy sauce, rice wine, white pepper, sesame oil, and sugar)
Pour sauce into wok and stir to combine
Thicken sauce with cornstarch slurry if needed
Stir few times and serve