In a medium saucepan over medium-high heat, cook the bacon until it is crisp and has released almost all of its fat, about 6 minutes. Add the onion, carrots, celery, salt, and pepper and cook, stirring frequently, until the vegetables are very soft and lightly browned around the edges, about 6 minutes. Add the ground chuck, ground veal, and ground pork and cook, stirring to break up any clumps, until the meat is browned, about 5 minutes. Add the white wine, garlic, and tomato paste and cook for 2 minutes, stirring constantly. Add the beef broth and bring to a boil. Lower the heat so that the sauce just simmers. Simmer, partially covered, for 10 to 15 minutes.