Step 1 Toss thinly sliced flank steak with 1 tablespoon soy sauce, 1 tablespoon cornstarch, and a splash of sesame oil in a bowl. Let it marinate for at least 15 minutes at room temperature.
Step 2 Blanch broccoli florets in boiling water for 60 to 90 seconds, then immediately transfer to an ice bath to stop cooking. Drain and set aside.
Step 3 In a small bowl, whisk together the remaining soy sauce, oyster sauce, beef broth, brown sugar, remaining cornstarch, and water to create the stir fry sauce. Set aside.
Step 4 Heat vegetable oil in a wok or large skillet over high heat until it just begins to smoke. Add the marinated beef in a single layer without crowding the pan. Sear for 1 to 2 minutes per side until browned. Remove beef and set aside on a plate.
Step 5 In the same wok, add minced garlic and grated ginger. Stir fry for 30 seconds until fragrant.
Step 6 Pour the prepared sauce into the wok and stir continuously until it thickens, about 1 minute.
Step 7 Return the seared beef and blanched broccoli to the wok. Toss everything together until evenly coated in the glossy sauce.
Step 8 Serve immediately over steamed jasmine rice. Garnish with toasted sesame seeds and sliced green onions.
