5 pound baby lamb shoulder with bone, cut in 2-inch cubes
2 ribs celery, coarsely chopped
2 medium carrots, coarsely chopped
1 large onion, sliced
1 cup dry white wine
½ cup olive oil
¼ cup balsamic vinegar
3 sprigs fresh rosemary
¼ teaspoon freshly ground pepper
½ teaspoon salt
2 cups beef stock
In a large bowl, toss all ingredients except the beef stock until well blended. Cover and refrigerate 24 hours, tossing occasionally.
Preheat the oven to 425 degrees. Transfer the contents of the refrigerated bowl to a roasting pan large enough to accommodate a single layer of vegetables covered by a single layer of meat. Add the stock and roast, basting and turning the lamb frequently, until the meat is very tender, about 1 hour 45 minutes.
Reduce the oven temperature to 350 degrees. Remove the lamb from the pan and set it aside. Skim and discard as much fat as possible from the pan liquids. Place the pan over high heat and boil until the liquid reduces to about 1 1/4 cups. Transfer the meat to a smaller roasting pan and strain the reduced sauce over it. Place the meat in the oven and roast, turning the meat every 10 minutes, until extremely tender, brown and caramelized, about 30-40 minutes.
Strain the juices from the pan and, if necessary, reduce further over moderately high heat; there should be 1/2 cup of finishing sauce. Transfer the lamb to a serving platter and spoon the sauce over it.