How to Make It
In a medium bowl, combine the apple juice, soy sauce, lemon juice, scallions, garlic, ginger and sesame oil. Put the short ribs in a large resealable plastic bag and pour the marinade into the bag. Seal the bag and transfer it to a metal baking pan. Refrigerate for at least 4 hours and up to 24 hours.
In a small skillet, heat the canola oil. Add the shallots, season with salt and cook over moderately high heat, stirring a few times, until lightly golden and softened, about 5 minutes. Transfer to a small bowl and let cool slightly.
In a blender or mini food processor, combine the cooked shallots with the garlic, scallions, miso, gochujang, vinegar, sesame oil and sugar and process to a smooth puree. Season the sauce with salt and transfer to a small bowl.
An hour before cooking, remove the marinated ribs from the refrigerator and let stand at room temperature.
Light a grill or preheat a grill pan. Remove the ribs from the marinade, scraping off any excess. Grill the ribs over moderately high heat, turning occasionally, until medium-rare, about 20 minutes. Let rest for 10 minutes, then thinly slice across the grain. Serve the ribs with the sauce and the sliced apple.