Slice the beef across the grain into 1/4-inch strips. (Partially frozen beef — 20–30 minutes in the freezer — slices much more easily.) Pat the strips very dry with paper towels; moisture is the enemy of a good sear. Toss with the black pepper.

Heat 1 tablespoon of the oil in a wok or large skillet over the highest heat until it just starts to smoke. Add half the beef in a single layer and sear undisturbed for 60–90 seconds, then toss and cook 1–2 minutes more until browned at the edges. Transfer to a plate. Repeat with the remaining beef. Doneness cue: thin strips cook through in a ripping-hot wok — check that no pink remains and a thermometer reads 160°F.

Add the remaining 1 tablespoon oil to the wok. Add the onion and carrots; stir-fry 2 minutes. Add the cabbage and stir-fry 2–3 minutes more, until it wilts but keeps a little crunch. The ripping-hot wok is what keeps the vegetables crisp-tender instead of soggy.

Push the vegetables to the sides of the wok. Add the garlic and ginger to the center and stir-fry 30–60 seconds, until fragrant but not browned.

Return the beef to the wok. Pour in the soy sauce, oyster sauce, and sesame oil; toss to coat. Stir the cornstarch slurry and drizzle it in, tossing until the sauce thickens and glosses over everything, about 1–2 minutes.

Spoon over hot rice, scatter with sesame seeds and green onions, and serve immediately.