Heat oven to 300°F. Pat ribs dry; season generously on both sides with salt and pepper. Wrap each rack in a double layer of foil, crimping edges tightly, and place on a rimmed baking sheet. Bake for 2 1/2 hours or until meat is soft but is not quite falling off the bone. Remove from oven and let sit inside foil until cool enough to handle.
In a food processor, pulse green onions, garlic, and ginger until finely chopped. In a medium saucepan over medium heat, heat oil. Add green onion, garlic, ginger mix and cook, stirring often, until golden, and starting to stick to bottom of pan, about 4 minutes. Add gochujang, ketchup, lime juice, plum sauce, sugar, shoyu, and water and stir until smooth. Bring to a simmer and cook, stirring often to prevent scorching, about 5-10 minutes until thick. Remove sauce from heat.
Heat outdoor grill on medium high heat; lightly oil grates. Remove ribs from foil and cut racks in half crosswise. Place ribs on grill, meaty side down, and grill until lightly charred, about 1 minute. Brush ribs with sauce and turn over. Brush with more sauce and continue to grill, turning ribs two more times, until sauce is lightly charred, about 2 minutes. Transfer to a cutting board and let rest 5 minutes before slicing into individual ribs. Serves 4.
Approximate Nutrient Analysis per serving (not including salt to taste):
900 calories, 61 g fat, 21 g saturated fat, 215 mg cholesterol, greater than 2200 mg sodium, 22 g carbohydrate, 1 g fiber, 8 g sugar, 54 g protein