Marinate the beef by combining the sliced flank steak with 2 tablespoons of low-sodium beef broth, 2 teaspoons of cornstarch, and 1/4 teaspoon of salt. Mix well and let marinate for about 10 minutes.

Prepare the sauce by whisking 1 cup of beef broth, 2 tablespoons of soy sauce, 2 tablespoons of oyster sauce, 2 tablespoons of cornstarch, 1 teaspoon of sugar, 1/4 teaspoon of Chinkiang vinegar, and 1/4 teaspoon of white pepper until smooth.

Cook the noodles in boiling water for about 4 minutes, drain, and let dry. Fry in a nonstick pan with 2 tablespoons of peanut oil, shaping into a patty until crispy.

In the same pan, heat 1 tablespoon of peanut oil and add marinated beef. Stir-fry until browned and slightly crispy, then set aside.

Add the remaining peanut oil to the pan, then toss in sliced yellow onion and carrot. Stir-fry until softened, then add minced garlic and ginger for another 30 seconds.

Add quartered baby bok choy and stir, cooking for another minute until slightly wilted.

Pour in the prepared sauce, stirring continuously until the sauce thickens for 2-3 minutes.

Mix in the beef, coating evenly and heating through for about 1 minute.

Serve by placing the crispy noodle patty on plates and spooning the beef stir-fry over it.