Combine the sliced flank steak, water, baking soda, cornstarch, oyster sauce, Shaoxing wine, and soy sauce. Marinate for at least 30 minutes.
Some fresh rice noodles come as large sheets, while others are already cut. If you have the sheets, slice the rice noodles so they're about 1 inch wide. If the noodles are very stiff and stuck together, bring a wok full of water to a boil, and add the noodles. Blanch them for 30 seconds to loosen. Transfer to an ice bath and drain thoroughly. If using dried rice noodles, soak in hot water for a few hours, or in cold water overnight.
Heat your wok over high heat until smoking, and add 1 1/2 tablespoons oil to coat the wok. Add the beef and sear until browned. As long as your wok is hot enough, the meat shouldn't stick. Set aside. Add 1 1/2 tablespoons more vegetable oil to the wok. Add the ginger to infuse the oil with its rich flavor for about 15 seconds. Add the scallions.
Spread the noodles evenly in the wok and stir-fry on high for about 15 seconds. Add the Shaoxing wine around the perimeter of the wok.
Next, add the soy sauces, sesame oil, sugar, and the seared beef. Stir-fry, making sure your metal wok spatula scrapes the bottom of the wok. Lift the noodles in an upward motion to mix well and coat them evenly with the sauce.
Add a bit of salt and white pepper to taste (taste the noodles before adding salt). Add the bean sprouts and stir-fry until they are just tender. Serve!
Notes
A useful tip is to freeze the beef before slicing, until it's firm but not solid. This makes slicing the beef much easier!Important: Heat should remain as high as possible at all times when cooking this dish.