01 - In a mixing bowl, combine gochujang, soy sauce, brown sugar, sesame oil, minced garlic, grated ginger, rice vinegar, mirin (if using), and black pepper. Whisk until the mixture is smooth and fully emulsified.
02 - Place the trimmed lamb ribs in a large resealable bag or shallow dish. Pour the marinade over the ribs, massaging to ensure every surface is evenly coated. Seal tightly and refrigerate for at least 4 hours, preferably overnight for maximum flavor penetration.
03 - Preheat the oven to 320°F. Remove the ribs from the marinade, reserving all excess marinade in a separate container. Arrange the ribs on a wire rack set over a rimmed baking sheet and cover tightly with aluminum foil.
04 - Roast the covered ribs in the oven for 1 hour. Meanwhile, pour the reserved marinade into a small saucepan, stir in the honey, and simmer over low heat for 5 minutes until the mixture reduces into a glossy glaze.
05 - Increase the oven temperature to 400°F. Uncover the ribs and brush them generously on all sides with the prepared glaze. Return to the oven uncovered and roast for 10 to 15 minutes until the surface is deeply caramelized and lightly charred at the edges.
06 - Remove the ribs from the oven and let them rest for 5 minutes. Squeeze fresh yuzu juice generously over the ribs, allowing the bright citrus to mingle with the caramelized glaze.
07 - Scatter sliced scallions, toasted sesame seeds, and sliced red chili over the ribs. Cut between the bones into individual portions and serve immediately with steamed rice or pickled vegetables.