01 - Heat olive oil in a large, heavy-bottomed pot over medium heat. Add onion, carrot, and celery. Sauté for 6–8 minutes until vegetables are softened and translucent.
02 - Stir in minced garlic and cook for 1 minute until fragrant, being careful not to burn it.
03 - Increase heat to medium-high. Add ground beef, breaking it up with a wooden spoon. Cook for approximately 8 minutes until completely browned and no pink remains.
04 - Stir in tomato paste and cook for 2 minutes to develop flavor. Pour in red wine, scraping up any browned bits from the bottom of the pot. Simmer for 2–3 minutes until slightly reduced.
05 - Add crushed tomatoes, beef stock, oregano, basil, bay leaf, salt, and pepper. Stir thoroughly to combine all ingredients.
06 - Reduce heat to low, cover partially with lid, and simmer gently for 45 minutes. Stir occasionally to prevent sticking and ensure even cooking.
07 - Stir in milk and continue simmering uncovered for 15 minutes. This allows flavors to meld and sauce to thicken slightly. Remove and discard bay leaf before serving.
08 - While sauce finishes, bring a large pot of generously salted water to a rolling boil. Cook spaghetti according to package directions until al dente. Drain well in a colander.
09 - Place cooked spaghetti on serving plates or in shallow bowls. Top generously with Bolognese sauce. Garnish with freshly grated Parmesan cheese and fresh basil or parsley leaves if desired.