In the bowl of the crockpot, season the short ribs with black pepper. Add the halved shallots, sliced ginger, and Chinese 5 spice, then pour over the pomegranate juice, tamari or soy sauce, and Thai chili sauce. Cover and cook on low for 6-8 hours or on high for 4-6 hours.
To make the oven version: Preheat the oven to 325° F. In a large oven-safe braiser, season the short ribs with black pepper, add the shallots, ginger, and Chinese 5 spice, then pour over the pomegranate juice, tamari or soy sauce, and Thai chili sauce. Cover and roast for 2 1/2 to 3 hours or until the short ribs are tender and falling off the bone.
Shred the ribs and discard the bones. Drain any excess grease away from the sauce, then toss the shredded ribs into the sauce and keep warm.
In a bowl, mix the chopped cilantro, chopped green onions, chopped roasted peanuts, and toasted sesame seeds. Add the pomegranate seeds if using.
Serve the ribs and sauce over rice and top with the cilantro–green onion–peanut mixture and pomegranate arils if using.