Slice beef thinly against the grain. Toss with baking soda, cornstarch, soy sauce, and cooking wine. Marinate for 20 minutes.

Rinse fermented black beans briefly and roughly chop them. Mix the sauce: combine oyster sauce, soy sauce, sugar, black pepper, and water.

Heat 1 tablespoon oil in a wok over high heat until smoking. Sear beef in a single layer for about 1 minute until browned. Remove to a plate.

Add remaining oil. Stir-fry garlic and chopped black beans for 30 seconds until very fragrant. Add onion and green pepper, stir-frying for 2 minutes until slightly softened but still crisp.

Return beef to the wok. Pour in the sauce and bring to a simmer. Drizzle in the cornstarch slurry and toss until the sauce thickens and glazes everything, about 30 seconds.

Serve immediately over steamed jasmine rice.