Cook the noodles according to package instructions. Drain and toss with 1 tbsp vegetable oil to prevent sticking.
Heat a large skillet or wok over medium-high heat. Add a bit of oil and spread the noodles in an even layer. Let them crisp undisturbed for 3–4 minutes, flip, and pan-fry the other side until golden. Remove and set aside.
In a bowl, marinate the beef with 1 tbsp soy sauce and 1 tsp cornstarch for 10 minutes.
In a separate bowl, mix the sauce ingredients: 2 tbsp soy sauce, oyster sauce, hoisin sauce, beef broth, and sugar.
Heat 1 tbsp vegetable oil in the skillet or wok. Add beef and stir-fry until browned. Remove and set aside.
Add garlic, bok choy, bell pepper, and bean sprouts to the skillet. Stir-fry for 2–3 minutes.
Return the beef to the pan, pour in the sauce, and stir to combine. Add the cornstarch slurry to thicken the sauce.
Add the pan-fried noodles and toss everything together until well coated and heated through. Garnish with green onions and a drizzle of sesame oil.
Serve hot and enjoy!