For the Pestata and Stuffing
2 cups milk
4 ounces bread
2 ounces pancetta, cut in chunks
1 large onion, cut in chunks
1 large carrot, cut in chunks
1 large rib celery, cut in chunks
3 garlic cloves, peeled
3 tablespoons extra-virgin olive oil
2 pounds sweet Italian sausage, loose or removed from casings
1 teaspoon kosher salt
1 cup dry white wine
1 large egg, lightly beaten
1 tablespoon Italian parsley, chopped
½ cup Parmigiano-Reggiano, grated
For the Cabbage Rolls and Sauce
1 medium head Savoy cabbage, about 2 pounds
¼ cup extra-virgin olive oil
2½ teaspoons kosher salt
3 cups dry white wine
4 cups chicken stock, hot
To make the stuffing, pour the milk over the bread chunks in a bowl, and let them soak for a few minutes, until completely saturated. Using a food processor, mince the pancetta, onion, carrot, celery, and garlic into a fine-textured pestata. You should have about 2 cups total. Pour the 3 tablespoons of olive oil into a heavy pan, and set over medium-high heat. Scrape in 1/2 cup of pestata, and cook for a few minutes, stirring frequently, until it starts to dry and stick on the pan bottom. Crumble the sausage into the skillet, and cook, stirring, until all the meat is sizzling and no longer pink, about 5 minutes. Season with 1 teaspoon salt, and pour in the white wine. Bring to a boil, and cook until the wine has evaporated completely. Remove from the heat, and immediately scrape the sausage into a large bowl to cool.
Meanwhile, preheat the oven to 375 degrees. Fill the big pot with water, and bring to a boil. When the meat has cooled, squeeze the milk from the soaked bread. Crumble the softened bread over the sausage, and combine them with your hands, then work in the beaten egg, chopped parsley, and grated cheese, tossing all together into a loose stuffing.
To prepare the cabbage, pull off and discard any bruised or torn outer leaves. Cut out the core of the cabbage, and separate the largest leaves from the head, keeping them intact. Lay each leaf flat, outside up, and with a sharp paring knife shave off the raised ridge of the rib at the leaf base. When you've trimmed twelve good-sized leaves (and a few extra) for the rolls, slice the remaining cluster of small inner leaves into shreds about 1/4-inch wide. Drop the big, trimmed leaves into the boiling water, and blanch them until soft and quite floppy, about 7 minutes. Cool them in a bowl of icy water; drain well, lay them on paper towels, and pat dry.
Return the sauté pan to the stove (wipe out any browned bits), pour in the 1/4 cup olive oil, and turn on medium-high heat. Stir in the remaining pestata, and cook until dried and sticking, about 4 minutes. Toss in all the shredded cabbage and 2 1/2 teaspoons salt, and cook, stirring, until the cabbage starts to wilt. Pour in the white wine, raise the heat to bring it to a boil, then lower heat and simmer the sauce for 10 minutes or so, to blend the flavors. As the sauce simmers, make the cabbage rolls.
Lay out each softened leaf with its shaved rib side down. Take about 1/3 cup stuffing in your fingers, form it into a plump log, and lay it on the leaf. Roll the bottom of the leaf over the filling, tuck the sides in, and roll up tightly the rest of the way.
When all the polpette are formed, lower the heat under the sauce and place each roll in the sauté pan, seam side down. Pour in the stock, submerging the rolls, heat to a bubbling boil, and put on the pan lid. Set the pan in the oven to braise the rolls for an hour. Remove the lid, and push the rolls down in the sauce, which will have reduced. Bake, uncovered, for another 30 minutes or so, until the sauce has reduced and thickened and the tops of the rolls are nicely caramelized.
Serve in a warm bowl with some of the sauce, accompanied by rice, potatoes, or polenta.