I saw this a few weeks ago on Lidia's tv show. Delicious! You could certainly do this ahead. It's as delicious, reheated the next day.
1 medium onion, cut in chunks
1 large carrot, cut in chunks
1 stalk celery , cut in chunks
10 fresh sage leaves
2 plump garlic cloves, peeled
5 tablespoons extra-virgin olive oil
2 teaspoons kosher salt
2½ pounds boneless, skinless chicken thighs, preferably 6 to 8 large thighs
6 slices bacon strips, thinly sliced, 2 inches wide
2 cups dry white wine
3 cups canned Italian plum tomatoes, preferably San Marzano, crushed by hand
3 tablespoons Grana Padano, or Parmigiano-Reggiano, grated
You will need a food processor; a heavy-bottomed, ovenproof skillet or sauté pan, 12-inch diameter or larger, with a cover; toothpicks.
Using a food processor, mince the onion, carrot, celery, 4 sage leaves, and the garlic into a fine- textured pestata. Pour 2 tablespoons of the olive oil into the big skillet, and set over medium heat. Stir the pestata into the oil, season with 1/2 teaspoon salt, and cook, stirring frequently, until it has wilted and just starts to stick to the pan bottom. Scrape all of the pestata into a bowl to cool.
Trim the chicken thighs of fat and any loose bits of flesh, and lay them open, boned side up, on a cutting board. One at a time, cover each thigh with a piece of plastic wrap, and pound it with a meat mallet (or other heavy implement) to an even thickness of about 1/2 inch. Sprinkle salt lightly on the flattened sides, using another 1/2 teaspoon in all.
Spread a tablespoon or so of the cooled pestata in a thin layer on each thigh, almost to the edges- use more or less depending on size. Fold the thighs over into thirds, as if folding a letter, and compress gently. Wrap a strip of bacon the long way around each bundle, so the open sides are partly sealed. Overlap the ends of the bacon and thread a toothpick through them to hold the strip in place.
Pour the remaining 3 tablespoons olive oil into the big skillet-cleaned of pestata-and set over medium-high heat. Lay all the chicken bundles in the pan, turning them when the bacon starts sizzling and rendering fat. Sauté the fagottini for 5 minutes or longer, turning several times, so the bacon and chicken are lightly caramelized all over. As they brown, drop the remaining pestata by spoonfuls in between the bundles, along with the rest of the sage leaves, to cook on the pan bottom.
When everything is sizzling, pour in the wine and bring to a bubbling simmer. Cook until the wine has reduced by half, turning the fagottini occasionally. Pour the crushed tomatoes (and juices) all over the bundles, and shake the pan to mix them with the wine. Season with the remaining teaspoon salt, and bring the braising liquid to a boil over high heat. Cover the pan, adjust the heat to keep things bubbling steadily, and braise until the thighs are cooked through and tender, 25 to 30 minutes, depending on size. (If you're not sure, slice discreetly into one of the bundles to check for doneness.)
If you want to finish the fagottini with a crisp gratinato topping, arrange a rack in the top part of your oven and preheat to 425 degrees while the chicken braises. When the meat is done, uncover the skillet, raise the heat, and reduce the braising liquid a bit, exposing the tops of the thighs. Turn off the heat, and carefully pull the toothpicks out of the bundles. Sprinkle a teaspoon or so of grated cheese over each, and set the skillet in the oven. Bake about 10 minutes, until the gratinato is golden, the bacon very crisp, and the sauce quite thick. Remove from the oven carefully.
To finish the fagottini on the stovetop: Reduce the braising juices in the uncovered pan a bit longer, until thickened to a sauce. Turn off the heat, pull out the toothpicks, sprinkle a teaspoon cheese over each, and set the cover back on for a minute, to melt the cheese.
To serve the fagottini: set one (or more if they're small) on a serving plate with sauce spooned around the hot bundle.