Heat the oven to 275°F. Sprinkle a good amount of salt and some pepper all over the ribs. Heat the oil in a large fry pan over medium-high heat. Brown the ribs, in batches if necessary, on all sides. Be sure there is room around the ribs so that they sear instead of steam and be patient, turning only after they have browned on one side, the browning step should take 10–12 minutes.
As the ribs are browned, transfer them to a dutch oven large enough to accommodate the meat and braising liquid. Leave about 2 tablespoons of the rendered fat in the skillet and pour off any excess. Return the fry pan to medium-high heat and add the onion, celery, carrot, and garlic. Cook, stirring, until the vegetables are tender and nicely browned, about 8 minutes. Add the red wine, thyme sprigs, bay leaves, peppercorns, coriander, and tomato and cook, stirring occassionally, until the liquid is reduced by half, about 15 minutes. Add the broth, bring to a boil and pour the liquid over the ribs in the baking dish. Cover the dutch oven and cook in the oven until fork-tender, 4 to 5 hours; some of the meat may fall off the bones, which is okay.
Let the meat cool in the braising liquid until it is almost room temperature. Transfer the ribs, meat side down, to another baking dish. Strain the braising liquid through fine-mesh strainer into a large saucepan. Ladle some of the braising liquid over the ribs to keep them moist; you want about 1/2 inch of liquid in the dish. If serving the ribs immediately, spoon off any fat you can see on the surface of the braised liquid. If not serving right away, refrigerate the ribs and the braising liquid separately, covered with plastic wrap until ready to serve. You can then remove the fat that has solidified on the top of the liquid once cooled, which is easier and more thorough.
To serve, heat the oven to 300°F. Bring the defatted braising liquid to a simmer over medium heat and cook, skimming occassionally, until reduced to about 1 1/3 cup, about 30 minutes. (If the reduction is done before the meat is sufficiently heated, just take it off the heat.) You don’t want to let the liquid come to a rolling boil, but you do want to see tiny bubbles coming to the surface. Meanwhile, gently reheat the ribs in the oven for 20 to 30 minutes. Just before serving, whisk the butter and chopped thyme leaves into the reduced braising liquid. Divide the ribs among six plates and top with the sauce.
5) Spoon the carrots and shallots – leave the Port and red wine shallot glaze in the pan – into a medium decorative casserole and rewarm in the oven for 5 minutes while the meat is resting. Place the shallot glaze over low heat and bring just to a boil. Place the chop on top of the vegetables, drizzle the meat with some of the shallot glaze and sprinkle with some fleur de sel. Serve immediately.