Make the marinade a day ahead, and let it sit in the fridge overnight, and then apply it to the meat on the second day.
Reprinted from Koreatown: A Cookbook. Copyright © 2016 by Deuki Hong and Matt Rodbard. Photographs copyright © 2016 by Sam Horine. Published by Clarkson Potter, an imprint of Penguin Random House, LLC.
Prepare the marinade: In a blender or food processor, combine the pineapple, onion, Asian pear, apple and garlic and puree until smooth.
In a large bowl, combine the puree with the soy sauce, sesame oil, sugar, mirin, sake and 4 cups of water. If you have the time, refrigerate the marinade for a day on its own. Add the short ribs and let marinate for at least 12 and up to 24 hours, in the fridge.
Remove the meat from the marinade and pat dry.
To pan-sear the meat: Preheat a large cast-iron skillet or grill pan, greased with a tablespoon of vegetable oil, over high heat until smoking hot. Working in batches, grill the marinated beef in one layer until cooked through, about 5 minutes, turning frequently until the meat begins to caramelize. Serve the meat as it is ready. Using kitchen shears, cut the meat into bite-sized pieces.
To grill the meat: Preheat a charcoal or gas grill on medium-high; you should be able to hold your hand 6 inches above the grill grate for only 3 to 4 seconds before you need to pull it away. Working in batches that fit comfortably in one layer, grill the short ribs until browned, about 3 minutes on each side. Using kitchen shears, cut the ribs into bite-sized pieces.
Serve the ribs with the rice, lettuce, perilla, kimchi and Ssamjang alongside. To eat, make a lettuce wrap (called ssambap): take a lettuce or perilla leaf in your palm and pack on a couple spoons of rice.
Layer with kimchi and a piece of short ribs and top with a dab of Ssamjang.