Step 1

In a food processor, combine the cilantro, ginger, garlic, hoisin, soy sauce, honey, five spice and 2 tablespoons of the gochujang. Process until smooth, about 2 minutes, scraping the bowl as needed. Remove 1 cup and set aside as a marinade for the ribs. Add the remaining 3 tablespoons gochujang and the lime juice to remaining mixture in the food processor and process until well combined. Transfer to a small bowl or glass measuring cup (you should have about 2 cups), cover and refrigerate for use as a glaze.

Step 2

Line a rimmed baking sheet with a double layer of plastic wrap. Set the ribs over it, then pour ½ cup of the marinade over each set, then use your hands to rub it into them on both sides. Wrap the plastic wrap around them and refrigerate for at least 8 hours or up to 24 hours.

Step 3

Heat the oven to 300°F with a rack in the middle position. Set a wire rack in a rimmed baking sheet. Lay an 18-by-36-inch sheet of heavy-duty foil on the counter.Unwrap 1 set of ribs and set in the center of and parallel with the foil. Fold the short ends up and over the meat, then the two long sides. Repeat with a second sheet of foil and remaining ribs. Set the wrapped ribs, foil seams up, on the prepared wire rack. Bake until a paring knife inserted between 2 rib bones meets little resistance, 2¼ to 2½ hours. Remove the baking sheet from the oven and increase the oven to 450°F.

Step 4

Carefully unwrap the ribs, reserving the accumulated juices. Place the unwrapped ribs, meaty side up, back on the rack. Pour the juices into a 2-cup liquid measuring cup or small bowl and let sit for 5 minutes. Using a spoon, skim off and discard any fat from the juices; you should have about 1½ cups defatted juices. Pour the juices into a medium saucepan over medium-high, bring to a simmer and cook until reduced to about ¼ cup, 15 to 20 minutes. Add the reserved 2 cups hoisin mixture and simmer over medium, stirring occasionally, until thickened and reduced to 1¾ cup, about 8 minutes.

Step 5

Generously brush the meaty side of the ribs with glaze and continue to bake, brushing every 8 to 9 minutes, until the glaze is darkened and charred in spots, about 30 minutes longer. Remove from the oven and evenly sprinkle the meaty side of each rack with half of the sesame seeds. Let rest for 30 minutes. Slice into individual ribs, then sprinkle with scallions. Serve with the remaining glaze.