Key to a successful stir fry: prep everything first. So start with cutting and slicing all ingredients.
Mix beef with soy sauce, shaoxing wine, brown sugar, oyster sauce, cornstarch and black pepper, mix well. Marinate for at least 15 minutes or up to 24 hours.
To cook, add oil and ginger in a large non-stick pan or wok. Cook on medium heat for 30 seconds then add garlic and fermented black beans.
Add marinated beef into the pan. Turn the heat up to high, cook undisturbed, turning once. Remove beef from the pan into a bowl and set aside.
Same pan, add white parts of green onion, bell peppers, onions and chilli (optional). Stir fry on high heat for 2 minutes.
Add beef back in, along with all the juices. Add green parts of green onion, and ~¼ cup of water. Season to taste, stir fry for a further 30 seconds.