Blend the grated pear, onion, garlic, and ginger with the pear/apple and pineapple juice until smooth.
Whisk in the soy sauce, sugar, sesame oil, sesame seeds, and black pepper.
Pour the marinade over the short ribs, turning to coat, and marinate overnight in the fridge for the deepest flavor.
Grill over high heat (charcoal is best for smokiness) 2-3 minutes per side until caramelized and cooked through.
Rest briefly, then serve with rice and banchan.
Home version adapted from Danny Kim's Instagram (featuring gui.nyc); the restaurant version sous-vides the ribs and ferments its own pear sauce, so quantities here are a standard home ratio.