Whisk the gochujang, pineapple juice, honey, sesame oil, ginger and garlic together in a medium bowl. Place the pork in a zip-top bag and pour the gochujang mixture over it. Seal the bag and shake well, making sure that the marinade coats the meat. Refrigerate for at least 6 hours or overnight. Heat a grill pan on medium-high heat or prepare an outdoor grill. Cook the pork until grill marks appear, about 3 minutes per side. Remove to a board and cut into bite-size pieces. On a serving platter, make separate piles of chiles, lettuce leaves and Korean Bean Sprout Salad. To make a lettuce cup, spoon some rice in the center of a lettuce leaf, top with a few pieces of pork, some chiles and salad, sprinkle with sesame seeds and fold.
Korean Bean Sprout Salad:
1 pound soya bean sprouts, with beans attached
1/4 cup sesame oil
2 tablespoons fish sauce
1 tablespoon gochugaru (Korean red chile pepper flakes)
1 tablespoon mirin
3 cloves garlic, minced
2 scallions, chopped
Sesame seeds, for garnish
Prepare a large bowl of ice water. Bring a large pot of salted water to a boil, and then add the bean sprouts and cook until al dente, about 1 minute. Remove with a slotted spoon and immediately add to the ice water. Drain in a strainer and pat dry. Add the bean sprouts to a medium bowl, toss with the sesame oil, fish sauce, gochugaru, mirin, garlic and scallions and sprinkle with sesame seeds.