Step 1: Slice the flank steak thinly against the grain.

Step 2: In a bowl, combine the sliced beef with 1 tablespoon soy sauce and 1 tablespoon cornstarch; mix and let marinate for 10 minutes.

Step 3: Bring a pot of water to a boil over high heat; blanch broccoli florets for 2 minutes, then drain and set aside.

Step 4: Heat 2 tablespoons vegetable oil in a wok or large skillet over medium-high heat until shimmering.

Step 5: Add the marinated beef to the pan and stir-fry for 3–4 minutes until browned.

Step 6: Add minced garlic and grated ginger; stir-fry for 30 seconds until fragrant.

Step 7: Return the blanched broccoli to the pan, pour in the remaining 2 tablespoons soy sauce, 2 tablespoons oyster sauce, and 1/4 cup beef broth; stir to combine.

Step 8: Mix the remaining 1 tablespoon cornstarch with 2 tablespoons water, pour into the pan, and cook for 1–2 minutes until the sauce thickens and coats the ingredients.

Step 9: Drizzle sesame oil (optional) over the stir-fry, toss to combine, and remove from heat.