How to Make It
Preheat the oven to 400°. Put the bread on a large baking sheet and brush all over with olive oil. Bake for about 20 minutes, until very crisp and golden brown. Let cool. Break up the toasts and transfer to a food processor. Process to coarse crumbs.
In a large glass measuring cup, cover the prunes with 1/2 cup of the wine. Microwave at high power for 1 minute, or until the prunes are soft. Cut the prunes into 1/2-inch pieces and transfer to a large bowl along with the soaking wine.
In a large, deep ovenproof skillet, heat the 1 teaspoon of olive oil. Add one-third of the pancetta and cook over moderate heat until crisp, about 7 minutes. With a slotted spoon, add the pancetta to the prunes. Add the garlic to the skillet and cook over low heat for 1 minute. Scrape the garlic into the bowl. Add the bread crumbs, chestnuts, chopped rosemary, pecorino and cayenne and season with salt and pepper. Stir in the eggs.
Put the steaks on a work surface and season both sides with salt and pepper. Press half of the stuffing over each steak. Roll up the steaks lengthwise and tie at 2-inch intervals with kitchen string.
Turn the oven down to 350°. Heat the remaining 1 tablespoon of olive oil in the skillet until shimmering. Add the steaks and cook over moderately high heat until browned all over, about 8 minutes. Turn the steaks seam side down. Add the remaining 3/4 cup of wine and pancetta to the skillet along with the broth, rosemary sprigs and shallots; bring to a boil. Transfer the skillet to the oven and braise the steaks for about 25 minutes, turning once, until a thermometer inserted in the steaks registers 130° for medium-rare to medium meat.
Transfer the steaks to a carving board to rest for 5 minutes. Whisk the flour into the pan juices and simmer over moderately high heat, whisking a few times, until the gravy is thickened and slightly reduced, about 3 minutes. Strain the gravy into a small saucepan, pressing on the solids. Season with salt and pepper and keep the gravy warm.
Untie the steaks and slice crosswise 1/4 inch thick. Serve with the gravy.