In a bowl, combine sliced beef with cornstarch, soy sauce, and a pinch of salt and pepper. Mix well and let it marinate for about 15 minutes.
In a large pan or skillet, heat 1 tablespoon of vegetable oil over medium-high heat. Add the marinated beef and sear for 3-4 minutes until browned. Remove the beef from the pan and set aside.
In the same pan, add the remaining vegetable oil. Add minced garlic and grated ginger, and sauté for about 30 seconds until fragrant.
Add the broccoli florets to the pan, stirring frequently for about 3-5 minutes until they turn bright green and are tender-crisp.
Pour the beef broth into the pan, followed by the oyster sauce (if using) and hoisin sauce. Stir well to combine.
Return the beef to the pan, and simmer everything together for another 3-4 minutes until the sauce thickens slightly.
Drizzle sesame oil over the dish, giving everything a final toss to combine the flavors.
Serve hot, garnished with sesame seeds and alongside cooked rice or noodles.
Notes
Feel free to adjust the sauce ingredients to taste.