In a mixing bowl, combine the sliced beef, dark soy sauce, and light soy sauce. Add the cornstarch and mix well until every slice is coated. The mixture should be sticky. Separate the beef slices that stick to each other and let marinade for at least 10 minutes.
To prepare the sauce, combine dark soy sauce, light soy sauce, shaoxing wine, oyster sauce, sesame oil, and sugar in a bowl and mix well until the sugar is fully dissolved. Set aside.
Cook the dried wide rice stick noodles according to packaging’s instructions (Our wide rice stick noodles needed to be boiled for about 4 and a half minutes). Drain off excess water and pour cold water over the noodles. Add about 1 tablespoon of vegetable oil to the noodles and mix well to avoid them from sticking to each other.
In a large pan or wok, heat about 1 and a half tablespoon of vegetable oil on medium high heat. Add the beef into the pan and cook for about 1 minute each side or until cooked thoroughly. Remove from heat and set aside.
In a large pan or wok, heat about 2 tablespoons of vegetable oil over medium high heat. Add the garlic, ginger, and scallions and stir fry until fragrant and tender. Add the onions and cook until fragrant, about 1 minute. Add the baby bok choys and stir fry until they are fully cooked and the onions are tender, about 3 to 5 minutes.
Place the cooked ingredients on one side of the pan to make place for the noodles. put heat on high and and add another tablespoon of vegetable oil and add the cooked noodles. Toss the noodles in the pan gently using tongs for about 30 seconds until they are well combined. Pour the sauce mixture over the noodles and mix well with tongs until all the noodles are uniform in color. Add the bean sprouts and and toss gently. Add in the cooked slices of beef and mix well. For a bit of char, let the ingredients sit for about 30 seconds to 1 minute on the pan without stirring. Remove from heat and serve.