3. Step
Heat a 14-inch flat-bottomed carbon-steel wok (or a 12-inch stainless-steel skillet) over high heat until a drop of water vaporizes within 1 to 2 seconds of contact. Swirl in vegetable oil. Add the beef in an even layer; cook, undisturbed, until it begins to brown, about 1 minute. Using a metal spatula, stir-fry until lightly browned but not cooked through, 30 seconds to 1 minute more. Transfer to a plate.