In a bowl, combine 1/2 cup olive oil with the sliced onion, carrot, and celery. Add the salt, crushed garlic cloves, bay leaves, rosemary, juniper berries, and the bottle of wine. Place the pork in a non-reactive bowl and cover with the marinade. Marinate for 3 days, refrigerated, stirring twice a day.
Remove the meat from the marinade.
In a large casserole, heat the remaining olive oil, then add the pork pieces and pancetta to sear on all sides, working in batches, and removing the meat once it is seared. Add the chopped onion and remaining garlic to the pan, and cook until just softened. Add the marinade and scrape the bottom of the pan with a wooden spoon. Add 2 cups wine and the pork and bring to a simmer. Cook over low heat, partially covered, for 90 minutes, or until the meat is very tender.
Remove the meat and keep it covered.
In a small saucepan, heat the sugar over high heat until it melts and turns golden. Remove from the heat and add the vinegar. Pour this mixture into the sauce and heat through. Serve the pork with the sauce spooned over. Encircle the pork with the Grilled Scallion Salad.
Drizzle the scallions with olive oil. Grill for 1 minute. Squeeze 1/2 lemon over scallions and grill for 2 more minutes. Season with salt and pepper. Remove the scallions from the grill and toss with the rest of the lemon juice.