Warm the olive oil In a large saucepan over medium-high heat. Add onion and vegetables and cook until tender, about 5 minutes.
Add the beef, season with salt and pepper, and cook for ten minutes, stirring to scrape up brown bits from the bottom of the pan.
Deglaze with the wine, and cook until it begins to evaporate.
Add the tomatoes, crushing them while stirring.
Add the parsley, and cook for another 10 minutes.
Add the beef stock and lower the heat.
Simmer until the sauce is rich and thick, 45 minutes - 3 hours. (The longer, the better!)
Serve over tagliatelle and top with freshly grated parmesan.