Instructions

Slice 8 ounces flank steak, trimmed, against the grain into ⅛-inch-thick and 2-inch-long pieces. Combine beef, 1 tablespoon soy sauce, 1 tablespoon Shaoxing wine, and ¼ teaspoon baking soda in bowl and gently stir until sauce is fully absorbed. Add 2 teaspoons cornstarch and mix again until evenly distributed. Let marinate for 15 minutes.
Combine ¼ cup chicken broth, 2 tablespoons oyster sauce, 2 teaspoons dark soy sauce, and 1 teaspoon sugar in small bowl.
Bring 2 quarts water to boil in large saucepan over high heat. Add 1½ cups macaroni, stirring often, until just al dente. Drain pasta, rinse with cold water, and drain again.
Heat 1 tablespoon peanut oil in wok over high heat until smoking. Add beef in single layer and cook until bottom side turns golden brown, 1 to 2 minutes. Flip and cook until second side is browned, 30 seconds to 1 minute. Transfer beef to plate.
Add remaining 2 tablespoons oil to now-empty wok and reduce heat to medium. Add 2 teaspoons grated ginger, 2 minced garlic cloves, and ¼ cup thinly sliced onion and cook, stirring constantly, until onion is light golden on edges, about 1 minute.
Add 1 head baby bok choy (stalks cut into ½-inch pieces, greens cut into 1-inch pieces); 4 cups bean sprouts; 4 scallions, cut into 2-inch pieces; and pinch table salt and cook, stirring constantly until vegetables are just starting to soften, about 30 seconds.
Gently toss macaroni to separate pieces, then stir into wok. Pour in sauce and mix until evenly coated. Add beef and cook, stirring constantly, until sauce is absorbed, 1 to 2 minutes.
Turn off heat and stir in 2 teaspoons toasted sesame oil. Transfer to serving plates and serve immediately.