01 - In a mixing bowl, combine the sliced beef with 1 tablespoon soy sauce, 1 tablespoon cornstarch, and 1 teaspoon sesame oil. Toss thoroughly and allow to marinate for 10 minutes.
02 - In a small bowl, whisk together 3 tablespoons soy sauce, 2 tablespoons oyster sauce, 2 tablespoons water, 1 tablespoon brown sugar, 1 teaspoon cornstarch, and 1/2 teaspoon black pepper until smooth. Set aside.
03 - Bring a pot of water to a boil. Add broccoli florets and blanch for 1 minute until bright green and just tender. Drain immediately and set aside.
04 - Heat 1 tablespoon vegetable oil in a large wok or skillet over high heat. Add the marinated beef in a single layer and sear for 1 to 2 minutes on each side until just browned. Remove beef from the pan and set aside.
05 - Add the remaining 1 tablespoon oil to the hot wok. Stir-fry garlic and ginger for about 30 seconds until aromatic.
06 - Add blanched broccoli to the wok and stir-fry for 1 to 2 minutes. Return the seared beef to the pan, tossing to combine.
07 - Pour in the prepared sauce. Stir and toss ingredients together for 2 to 3 minutes, allowing the sauce to thicken and coat the beef and broccoli evenly.
08 - Garnish with sliced scallions if desired. Serve hot with steamed rice.