1. Add onion, celery, carrot and garlic to a food processor. Pulse several times until vegetables are in very small pieces. Heat oil in a large saute pan over medium-high heat. Add sausage, beef and veal. Cook 8 minutes, stirring occasionally and breaking up meat. Add vegetables; cook 5 minutes. Pour in wine. Bring to a simmer and cook 2 minutes, scraping bottom of pan to release any brown bits. Stir in tomatoes and bay leaf. Reduce heat to medium-low and simmer 15 minutes. Remove bay leaf. Stir in salt and pepper.
2. Meanwhile, bring a pot of lightly salted water to a boil. Add pasta and cook according to package directions. Drain and stir into Bolognese sauce.
3. If desired, garnish each serving with a large dollop of ricotta and chopped parsley.