Put the soy sauce, sesame oil, sugar, garlic, onion and pear in a food processor and pulse until smooth with some small chunks remaining.
Put the meat in a zip-top bag and add the marinade. Seal the bag and shake well to incorporate the marinade with the meat. Add the sesame seeds and scallions, reseal the bag and place in the refrigerator to marinate for at least 6 hours or overnight.
Heat a grill pan on high heat or prepare an outdoor grill. Remove the beef from the marinade and grill for 2 minutes per side.
Place the meat on a serving platter and surround with separate piles of kimchi, lettuce leaves, miso paste and white rice. Use the lettuce as a cup and fill with the remaining ingredients.