Season the lamb chunks with salt and pepper and add to the skillet. Increase the heat to high and sear the lamb on all sides; work in batches if necessary to avoid overcrowding the pan. Stir in the wine, scraping the bottom of the pan with a wooden spoon to incorporate the browned bits of meat and onion, and season with salt and pepper. Cover and cook over medium-low heat for about 1 1/2 hours, until the meat is very tender. Add more wine or water if necessary to keep the pan from drying out.