01 - Combine sliced flank steak with 1 tablespoon soy sauce, 1 teaspoon cornstarch, and 1 teaspoon sesame oil. Mix thoroughly and let marinate for 10 minutes.
02 - Whisk together soy sauce, oyster sauce, hoisin sauce, dark soy sauce if using, brown sugar, sesame oil, water, and cornstarch until smooth. Set aside.
03 - Cook lo mein or egg noodles according to package directions. Drain, rinse under cold water, and set aside.
04 - Heat 1 tablespoon vegetable oil in a large wok or skillet over high heat. Stir-fry marinated beef for 2 to 3 minutes until just cooked. Remove and set aside.
05 - Add remaining 1 tablespoon vegetable oil to the wok. Stir-fry minced garlic, ginger, and sliced onion for 1 minute until fragrant.
06 - Add broccoli florets and julienned carrot. Stir-fry for 2 to 3 minutes until tender-crisp.
07 - Return beef to the wok with cooked noodles. Pour in the prepared sauce and toss to combine. Stir-fry for 2 to 3 minutes until heated through and evenly coated.
08 - Drizzle with extra sesame oil. Sprinkle sliced green onions and toasted sesame seeds over the top. Serve immediately.