How to Make It
In a large enameled cast-iron casserole, heat the oil until almost smoking. Season the pork with salt and pepper and put it in the hot oil, meaty side down. Brown the pork over moderate heat on the 3 meaty sides, about 4 minutes per side. Turn the pork so the rib bones are on the bottom. Add the shallots, rosemary and 1/2 cup of water. Cover and cook over low heat, turning the shallots occasionally, until the shallots are tender; start checking after 30 minutes.
Meanwhile, put the potatoes in a medium saucepan and cover with water. Add a large pinch of salt and bring to a boil. Boil over moderately high heat until almost tender, about 8 minutes. Drain.
When the shallots are done, transfer them to a warmed serving bowl. Add 1/4 cup of water to the casserole and continue to braise the pork for 1 hour longer, or until an instant-read thermometer inserted in the center registers 145°. Transfer the pork to a carving board and cover loosely with foil.
Pour the pan juices into a glass measuring cup and discard the rosemary. Skim off the fat from the juices and reserve in a bowl. Add 3 tablespoons of the reserved fat to the casserole and heat. Add the shallots, season with salt and pepper and cook over moderate heat until lightly browned, about 3 minutes; return to the bowl and cover.
Add 1 more tablespoon of the reserved fat to the casserole. Add the potatoes, cut side down, and season with salt and pepper. Add 2 tablespoons of water, cover and cook until the potatoes are tender and browned on the bottom, about 8 minutes. Using a metal spatula, scrape the potatoes from the casserole and add them to the shallots.
Add 1/4 cup of water to the casserole and boil over high heat, scraping up the browned bits on the bottom. Add the pan juices and bring to a boil. Strain into a sauceboat and season with salt and pepper. Carve the roast and serve with the potatoes and shallots. Pass the pan juices and condiments at the table.