Place the pork loin on a cutting board.
Peel, trim, and cut the garlic cloves into one-half-inch chunks.
With a slim paring knife, make an incision in the pork, about 1 inch deep. Insert a piece of garlic and push it in deeply with your finger. Make another incision and press a peppercorn into it. Continue to stud the meat, turning it frequently, so that it is "larded" all over with the remaining garlic chunks and peppercorns. Season the loin with 1 teaspoon of the salt, rubbing it into the meat.
Wash, trim, and coarsely chop the tomatoes. Peel, trim, and finely dice the onion.
Preheat the oven to 350 degrees Fahrenheit
In a large skillet, sauté the onion in the olive oil over medium heat, stirring, until translucent. Add the wine and cook until it almost evaporates. Add the tomatoes, oregano, and thyme, stir to combine, and cook for a few minutes, until the tomatoes release some water. Stir in the chicken broth and cook, stirring occasionally, for 10 minutes more. Bury the parsley in the sauce and add the remaining one and a half of teaspoons salt.
Place the pork loin in a shallow roasting pan and pour the hot tomato sauce over it. Cover tightly with aluminum foil, place it in the oven, and braise for two and a half hours to 3 hours, bathing it every now and then with the sauce. The pork should be very tender, and the sauce mushy and thick. Remove from the oven, and let the dish come to room temperature.
When ready to serve, remove the pork from the sauce and slice it thick, about one and a half inches per slice. Use a sharp knife because the meat will be almost falling apart. Return the slices to the roasting pan. Remove and discard the parsley. Scrape the sides and bottom of the pan and spoon the sauce over the pork. If the sauce is too thin at this point, transfer the pork to a platter and reduce the sauce over medium heat to the desired consistency. This may be served as soon as it is finished, while it is still hot, or it can be held at room temperature for serving within 1 hour of finishing.