01 - Heat olive oil in a large, heavy-bottomed pot over medium heat. Add onion, carrot, and celery. Sauté for 6-8 minutes until softened and fragrant.
02 - Stir in minced garlic and cook for 1 minute until fragrant, being careful not to burn.
03 - Add ground beef, breaking it up with a wooden spoon. Cook until browned and no longer pink, about 8 minutes.
04 - Pour in red wine. Simmer for 2-3 minutes, scraping up any browned bits from the bottom of the pot.
05 - Stir in tomato paste, crushed tomatoes, beef broth, oregano, basil, bay leaf, salt, and pepper. Bring to a gentle simmer.
06 - Reduce heat to low. Partially cover and simmer for 45-60 minutes, stirring occasionally, until sauce thickens and flavors meld together.
07 - Stir in milk or cream during the last 10 minutes of simmering for extra richness. Adjust seasoning to taste.
08 - Meanwhile, cook spaghetti in a large pot of salted boiling water until al dente. Reserve 1/2 cup pasta water, then drain.
09 - Discard bay leaf from sauce. Combine spaghetti and sauce, adding reserved pasta water if needed for desired consistency. Serve hot, topped with grated Parmesan and parsley.