Blot the beef dry with paper towels and place in a bowl. Mix all marinade ingredients (soy sauce, brown sugar, mirin, sesame oil, grated onion, garlic, grated apple, ginger, and pepper) in a small bowl, then pour over the beef and stir gently to coat. Cover and marinate for at least 1 hour, preferably overnight.

Heat the cooking oil in a wok or large skillet over high heat until shimmering.

Add the sliced onion and white scallion parts to the wok and cook for 1 minute, stirring frequently.

Add the marinated beef along with the marinade and the sliced carrots. Cook for 3-5 minutes, stirring constantly, until the beef is cooked through and the sauce has slightly caramelized.

Remove from heat and toss through the sesame seeds. Serve immediately over steamed rice, garnished with the reserved green scallion parts.