Korean
Freeze the beef for 30 minutes, then slice it as thinly as possible against the grain.
Whisk together soy sauce, brown sugar, grated pear, sesame oil, garlic, ginger, and black pepper.
Toss the beef in the marinade and refrigerate for at least 30 minutes, ideally a few hours.
Heat a large skillet or grill pan over high heat until very hot.
Add the beef in a single layer and sear quickly, working in batches so it caramelizes rather than steams.
Stir in most of the green onions during the last minute of cooking.
Serve hot, topped with sesame seeds and the remaining green onions, alongside steamed rice.