Preheat the oven to 300 degrees. Season the meat with salt and pepper. Place the meat in an oven proof pan and cover with the lamb fat. Add the garlic cloves and rosemary sprigs to the pan and season with salt and pepper. Cover the pan with aluminum foil and place in the oven. Slow cook the meat for about 2 to 2 1/2 hours or until the meat is very tender. Remove from the oven and strain. Reserve the lamb fat for future use. Discard the rosemary. Place the meat in a mixing bowl, and using two forks begin to separate the meat into strands. This is called pulling the meat. Stir 1/4 cup of the duck fat. Stir in the shallots, garlic, rosemary and parsley. Season the lamb with salt and black pepper. If the rillette is not moist enough, add the remaining duck fat. Cover the rillette and store in the refrigerator. The rillette will keep for up to 2 weeks.