01 - Combine flank steak with 1 tablespoon soy sauce, cornstarch, and 1 teaspoon sesame oil. Allow to marinate for 10 minutes.
02 - Cook lo mein noodles following package directions. Drain, rinse under cold water, and set aside.
03 - Whisk together soy sauce, oyster sauce, hoisin sauce, rice vinegar, sesame oil, sugar, and black pepper in a small bowl.
04 - Heat 1 tablespoon oil in a wok or large skillet over high heat. Stir-fry marinated beef for 2 to 3 minutes until browned. Remove and set aside.
05 - Add another tablespoon of oil to the pan. Stir-fry broccoli and bell pepper for 2 to 3 minutes until tender-crisp. Add garlic and ginger, cooking 30 seconds until aromatic.
06 - Return beef to the pan along with cooked noodles. Pour sauce over and toss for 2 to 3 minutes until noodles are coated and heated through.
07 - Stir in sliced green onions, remove from heat, garnish with toasted sesame seeds, and serve immediately.