Cook the egg noodles according to package instructions, then drain.
Slice the flank steak thinly against the grain and marinate with soy sauce, cornstarch, and a splash of sesame oil.
Heat a wok or large skillet over high heat and add a tablespoon of oil.
Add the marinated beef to the hot wok and cook until browned, about 2-3 minutes, then remove and set aside.
In the same wok, add a bit more oil, then stir-fry garlic, broccoli, and red bell pepper for about 2-3 minutes until slightly tender.
Return the beef to the wok along with the cooked noodles, beef broth, oyster sauce, and the remaining sesame oil, tossing everything to coat.
Continue to stir-fry for another 3-4 minutes until everything is heated through and the noodles are well-coated with sauce.
Garnish with chopped green onions before serving.
