Season the shanks generously on all sides with the salt and black pepper.
Place the flour on a large plate. Dredge the shanks in the flour and shake to remove any excess.
Heat a Dutch oven or large, heavy saute pan over high heat. Add the shanks and sear until well-browned on all sides, about 8 minutes. Remove the shanks. Add the onions, carrots, and celery, and cook, stirring, for 4 minutes. Add the garlic and cook, stirring, for 1 minute. Add the wine and cook, stirring, to deglaze the pan. Cook until slightly reduced, about 5 minutes. Return the shanks to the pot and add the stock, bay leaves, and rosemary, and bring to a boil. Reduce the heat to medium-low, cover with the lid slightly ajar, and simmer until the shanks are tender, about 1 hour and 45 minutes to 2 hours, skimming to remove any scum that forms on top.
Preheat the oven to 375 degrees F.
Remove from the heat and discard the bay leaves. Transfer the shanks to a large plate and let rest until cool enough to handle. Transfer the braising liquid and vegetables to a medium pot and bring to a boil. Reduce the heat to medium-low and simmer until reduced by 1/3 in volume, about 30 minutes, skimming the top occasionally to remove any scum. Remove from the heat.
To make the Gorgonzola Crust, combine the bread crumbs, Gorgonzola cheese, egg, thyme, 1/4 teaspoon salt, and 1/4 teaspoon black pepper in the bowl of a food processor. Pulse several times until the mixture resembles wet sand. Transfer to a medium bowl.
Line a baking dish with foil.
When the shanks are cool, coat evenly with the Dijon mustard. Dredge 1 at a time in the Gorgonzola crust, pressing down to adhere about 1/3 cup of the crust to the meat. Reserve the remaining crust mixture. Place the shanks in the prepared baking dish and bake until golden brown, 20 to 25 minutes.
Add the remaining crust mixture to the reduced braising liquid and simmer over medium heat for 6 minutes. Remove from the heat. With a hand-held immersion blender or in batches in a food processor, puree the liquid on high speed. Cover to keep warm until ready to serve, then transfer to a gravy boat or decorative bowl.
Remove the shanks from the oven. Drizzle with the sauce, and pass the remaining sauce at the table. Serve with Rosemary Creamed Potatoes. Serve immediately.
Rosemary Creamed Potatoes:
Preheat the oven to 250 degrees F.
Combine the potatoes and 1 teaspoon of salt in a heavy, medium pot. Cover with water by 1-inch and bring to a boil. Cook until the potatoes are just fork tender, 10 to 12 minutes. Drain in a colander and spread in a layer on a baking sheet. Bake until dry, 10 minutes.
Remove from the oven and transfer to a heavy, medium pot. Over medium heat, add the remaining ingredients, and with a hand-held potato masher, mash the potatoes until creamy and the ingredients are well blended. Remove from the heat and transfer to a casserole dish. If preparing for the next day, allow to cool to room temperature and refrigerate, covered with plastic wrap, until the following day.
Remove from the refrigerator and allow to warm to room temperature. Replace the plastic wrap with aluminum foil and bake for 25 to 35 minutes, until hot throughout. Remove from the oven, stir well to fluff potatoes, then serve immediately.