01 - Heat olive oil in a large heavy-bottomed pot over medium heat. Add chopped onion, diced carrots, and diced celery. Sauté for 6-8 minutes until vegetables are softened and fragrant.
02 - Stir in minced garlic and cook for 1 minute until fragrant, being careful not to burn it.
03 - Add ground beef to the pot, breaking it up with a wooden spoon. Cook for approximately 8 minutes until thoroughly browned and no longer pink.
04 - Pour in red wine and simmer for 2-3 minutes, scraping up any browned bits from the bottom of the pot to incorporate the fond.
05 - Stir in tomato paste, crushed tomatoes, beef broth, dried oregano, dried basil, bay leaf, salt, and pepper. Bring mixture to a gentle simmer.
06 - Reduce heat to low, partially cover, and simmer for 45-60 minutes. Stir occasionally until sauce thickens considerably and flavors have melded together.
07 - Stir in milk or cream during the final 10 minutes of simmering for added creaminess. Taste and adjust seasoning as needed.
08 - While sauce simmers, cook spaghetti in a large pot of salted boiling water until al dente. Reserve 1/2 cup pasta water before draining.
09 - Remove and discard bay leaf from sauce. Toss drained spaghetti with the Bolognese sauce, adding reserved pasta water if needed to achieve desired consistency. Serve immediately topped with grated Parmesan and fresh parsley.