Thinly slice the flank steak against the grain and on a bias. See how I do this in the video.
Add the steak to a medium-sized bowl and mix it together with the egg, soy sauce, Shaoxing wine, oil, pepper, cornstarch, and baking soda. Set it to the side to marinate.
In the meantime, prepare the bell peppers, onions, green onions, garlic, and ginger.
To make the sauce, mix together the beef stock, soy sauce, oyster sauce, Shaoxing wine, sugar, lemon juice, and cornstarch until combined. Set it to the side.
Add the 3 tablespoons of oil to a large wok over high heat and heat until it begins to smoke lightly.
Place in the marinated steak and immediately push it up the sides to cover more surface area to sear the steak. Cook for 1 minute.
Stir fry the beef by placing a ladle, spoon, or metal spatula in the center of the pan and, using your other hand rock the pan back and forth to stir and while frying. Do this for 1 to 2 minutes or until the beef is cooked. Set it to the side on a plate.
Add 1 teaspoon of oil to the same wok over high heat and stir fry the peppers and onions for 30 to 45 seconds.
Stir in the garlic and ginger for 30 seconds.
Add back in the cooked steak.
Pour in ½ to 2/3 of the sauce and stir fry for 10 to 20 seconds to see if the ingredients are completely coated. If you enjoy more sauce, add the remaining. It is better to add a little at a time until the desired amount of sauce is achieved.
Finish by stirring in the green onions.
Notes
Make-Ahead: This is meant to be eaten as soon as it’s done cooking.How to Store: cover it and keep it in the refrigerator for up to 3 days. You can freeze this covered for up to 3 months. Thaw it in the refrigerator for 1 day or until thawed.How to Reheat: Add the desired amount of pepper steak back to a hot wok with 1 to 2 tablespoons of oil and stir fry for 2 to 3 minutes or until hot.You can cook this in a large cast iron or non-stick skillet if you do not have a wok.If there is still some oil left over from stir-frying the steak, there is no need to add more when cooking the peppers and onions.Dry sherry is also a great substitute for the Shaoxing wine.