Season the ribs with salt and pepper and refrigerate for at least 6 hours before cooking. Ideally overnight.
Bring to room temperature and season again with salt and pepper.
Preheat your oven to 350. Heat a large sautepan over high heat until it is very hot. This is critical for searing the meat. Add the olive oil and heat for a minute or so until it is super hot. In batches, sear ribs on all sides, turning them as necessary. Do this until they are all browned on all sides. Transfer the ribs to a large Dutch oven. Pour off most of the fatty liquid from the pan, try to keep about 2 Tablespoons in the pan. You will use this to saute the vegetables. Turn the heat to medium and saute the onion, celery, carrot and garlic. Saute for about 5 minutes, you want the onions to be slightly carmelized for texture and flavor. Add the wine, bay leaves and thyme. Bring to a boil and reduce wine by half. This takes about 7-10 minutes. Add the beef stock and bring to a boil. Once it is boiling, add all of this to the Dutch oven covering the ribs. Cover. Place this in the oven and let cook for 2.5 hours. Skim off any extra fat from the surface. All the ribs to cool in the liquid until they can be handled. Remove the meat from the bones, discard the bones. Return the meat to the Dutch oven.
Now, in a medium saucepan, boil salted water and add the potatoes. Cook until tender, about 15 minutes. Drain and dry them in the pan over low heat. Then pass them through a ricer, back into the pan. Ricers are incredible for the smoothest mashed potatoes. If you don't have one - go get yourself a present!
In a small saucepan, heat the milk and butter together until hot but not boiling. Pour this into the potatoes. Add the egg yolk; fold all together thoroughly.
Raise the oven to 400. Transfer contents of Dutch oven to a 9x13 baking dish or divide among individual gratin dishes. Cover the meat creation with potatoes as evenly as possible. Drizzle with Olio D' Natalia. Bake until topping is golden, 35-40 minutes. Serve immediately with a glass of Fritz Estate Reserve Zinfandel - this dish and this wine were meant to be together.