In a large casserole or Dutch oven, heat the olive oil until almost smoking. Add the pancetta and sauté for 2 minutes. Add the onion and sauté for 2 minutes. Remove the pancetta and onion with a slotted spoon, reserving on a plate. Add the veal pieces and brown them on all sides, then remove to a plate, working in batches if necessary to avoid overcrowding the pan. When all of the veal has been browned, add the tomato sauce and wine and bring to a boil, scraping the bottom of the pan to loosen the browned bits. Reduce to a simmer and add the veal, onions and pancetta. Cover tightly and simmer for 1 hour. Allow to rest 10 minutes off the heat before serving.