Slice the beef into thin strips against the grain. In a bowl, combine the beef with 1 tablespoon of soy sauce and 1 teaspoon of cornstarch. Let marinate for 10 minutes.
While the beef marinates, blanch the broccoli in boiling salted water for 2 minutes, then drain and set aside.
In a small bowl, whisk together the remaining soy sauce, oyster sauce, hoisin sauce, sugar, black pepper, and water or broth. Set aside.
Heat 1 tablespoon of oil in a large skillet or wok over high heat. Add the marinated beef and stir-fry for 2–3 minutes until browned but not fully cooked. Remove and set aside.
Add the remaining 1 tablespoon of oil to the same pan. Stir in garlic and ginger, cooking for 30 seconds until fragrant.
Add the blanched broccoli to the pan and stir-fry for 1–2 minutes. Return the beef to the pan.
Pour the sauce mixture over the beef and broccoli. Toss everything together and cook for another 1–2 minutes until the sauce thickens slightly.
Garnish with sliced green onions and serve immediately over steamed rice.
Notes
Serve hot with steamed jasmine rice for a complete meal.