1. Preheat oven to 300°F. Season ribs generously on both sides with salt and pepper then wrap with tin foil and place on a rimmed baking sheet. Bake for 2–2½ hours until meat yields. Leave to sit in foil outside the oven until cool enough to handle.
2. Meanwhile, pulse garlic and ginger in a food processor. Heat oil in a saucepan. Add mixture and cook for 4 minutes. Add gochujang, ketchup, lime juice, plum sauce, sugar, fish sauce, soy sauce and ¼ cup water. Bring to a simmer and stir for 10 minutes then remove from heat.
3. Heat a grill to medium-high and oil lightly. Cut rib racks in half then place ribs on grill, meaty side down for 1 minute. Brush ribs with sauce and then turn. Repeat this step three times until sauce is charred. Allow ribs to rest for 5 minutes before slicing.