Slice your flank steak or sirloin against the grain into thin slices, roughly 1/8 inch thick.

Bring a large pot of salted water to a boil and cook your lo mein noodles according to package directions, usually 4 to 5 minutes. Drain and set aside.

In a small bowl, whisk together soy sauce, oyster sauce, sesame oil, rice vinegar, white pepper, cornstarch, and broth until the cornstarch dissolves.

Heat a wok or large skillet over high heat until smoking.

Add 1 tablespoon of vegetable oil, then add half of the beef slices in a single layer. Sear for 2 to 3 minutes without stirring until browned.

Stir the beef and cook for another minute, then transfer to a plate. Repeat with another tablespoon of oil and the remaining beef.

Add the last tablespoon of oil, garlic, and ginger to the wok. Cook for 30 seconds to 1 minute until fragrant.

Add carrots and bell peppers first. Stir-fry for 2 to 3 minutes until tender but still crunchy.

Add bok choy and cook for another 1 to 2 minutes until wilted but bright green.

Return the beef to the wok along with the noodles. Pour in the prepared sauce and toss for 1 to 2 minutes to coat.

If noodles seem dry, add a splash of broth or water and toss again.

Transfer to serving bowls and top with sliced green onions. Serve immediately.