Marinate the Beef : In a bowl, combine the flank steak with soy sauce, oyster sauce, Shaoxing wine, and cornstarch. Mix well until the beef is evenly coated. Let it marinate for 10–15 minutes while you prepare the other ingredients.

Prep the Rice Noodles : If using fresh rice noodles, gently separate them with your hands. For dried rice noodles, cook according to the package instructions, rinse under cold water, and set aside.

Stir-Fry the Beef : Heat 1 tablespoon of vegetable oil in a large wok or skillet over high heat. Once hot, add the marinated beef and stir-fry for 2–3 minutes until browned and cooked through. Remove from the wok and set aside.

Cook the Vegetables : In the same wok, add the remaining 1 tablespoon of vegetable oil. Toss in the green onions, yellow onion, and bean sprouts. Stir-fry for 1–2 minutes until slightly softened.

Combine Everything : Add the rice noodles to the wok with the vegetables. Drizzle with dark soy sauce and sesame oil, then toss to coat the noodles evenly. Return the cooked beef to the wok and stir everything together. Cook for another 1–2 minutes until everything is well combined and heated through.

Serve : Remove from heat and transfer the Beef Chow Fun to a serving plate. Garnish with additional green onions if desired. Serve hot and enjoy!