Place the beef in the freezer for 30 minutes to firm it up, then use a sharp knife to slice it paper-thin against the grain. Pat slices dry with paper towels.

In a large bowl, whisk together soy sauce, grated pear with its juice, brown sugar, sesame oil, garlic, ginger, rice wine, and black pepper until sugar dissolves.

Add beef slices to the marinade, tossing with your hands to coat every piece. Cover and refrigerate for at least 30 minutes, or up to 4 hours for deeper flavor.

Heat a large cast-iron skillet or grill pan over high heat until smoking. Working in batches to avoid crowding, cook beef in a single layer for 1-2 minutes per side until caramelized and an instant-read thermometer inserted into the thickest piece reads 145°F (63°C). Transfer to a platter and repeat.

Pile the cooked bulgogi onto a serving plate, sprinkle generously with sesame seeds and scallions. Serve immediately with steamed rice, lettuce leaves, and ssamjang.