Thinly slice the flank steak against the grain and on a bias. 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.
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.