Silky sliced beef is stir-fried with a rich, glossy oyster sauce and tender vegetables. This high protein Chinese staple is quick enough for weeknight family cooking and incredibly versatile.
Slice the flank steak thinly against the grain and toss with 1 teaspoon of cornstarch for tenderness; set aside.
Mix oyster sauce, soy sauce, sugar, and remaining cornstarch with 1/4 cup water in a bowl to create the stir-fry sauce.
Heat 1 tablespoon vegetable oil in a large skillet or wok over high heat; add garlic and stir-fry for 10 seconds until fragrant.
Add the beef in a single layer and sear on high heat for 1 minute without stirring; then stir-fry for another minute until just browned, remove to a plate.
Add the remaining oil; toss in broccoli, carrot, and green onion. Stir-fry over medium-high heat for 2 minutes, adding a splash of water if the pan is dry.
Return the beef to the pan, pour in the sauce, and stir-fry everything together on high heat until the sauce is glossy and thickened, 1–2 minutes.
Season with black pepper, toss well, and serve immediately for best flavor and silky texture.