How to Make It
In a large resealable plastic bag, combine the soy sauce, mirin, lime juice, brown sugar, ginger and garlic. Cut the pork belly in half crosswise, roughly into two 6-inch squares. Add the pork belly to the marinade and seal the bag, pressing out any excess air. Refrigerate overnight.
Preheat the oven to 325°. Remove the pork from the bag and pat dry with paper towels; reserve the marinade. In a large enameled cast-iron casserole, heat the oil. Add the pork and cook over moderately low heat, turning occasionally, until browned all over, about 10 minutes; transfer to a plate.
Pour off all but 1 tablespoon of fat from the casserole. Add the onion, season lightly with salt and cook over moderate heat, stirring, until softened, about 5 minutes. Add the marinade and chicken broth and scrape up any bits stuck to the bottom of the casserole. Return the pork to the casserole and bring to a boil. Cover and braise in the oven for 2 hours, until the meat is nearly tender. Uncover and braise for 1 hour longer, until the meat is very tender.
Transfer the pork to a baking sheet fat side up. Strain the broth into a heatproof bowl and spoon off the fat. Return the broth to the casserole and simmer until reduced to 2 cups, about 5 minutes.
Preheat the broiler. Broil the pork 8 inches from the heat until crisp, about 2 minutes; cut it into twelve 1/2-inch-thick slices and arrange in shallow bowls. Spoon the broth all around and garnish with the scallions. Serve with Pickled Radishes and rice.