1. Heat the butter and oil in a heavy saucepan or earthenware pot. Add the onion, and cook over moderate heat for 3 to 4 minutes. Add the pancetta and cook untion the onion is translucent. Stir in the carrot, celery, and garlic. Cook 3 to 4 minutes more.
2. Add the beef, and crumble it into the vegetables with a fork. Stir until the meat loses its red color. Season with salt and pepper.
3. Pour in the wine, raise the heat slightly, and cook until the liquid evaporates, 3 to 4 minutes. Add the milk, and cook until it evaporates.
4. Stir in the tomatoes with their juice, and the herbs. Bring the sauce to a boil. Reduce the heat to low, and simmer, uncovered for 1 1/2 to 2 hours, stirring occasionally. Correct the seasoning before serving. Serve over pasta.