In a large Dutch oven, heat olive oil and butter over medium-low heat. Add pancetta and cook until golden and crisp.

Finely mince yellow onion, carrots, celery ribs, and garlic cloves in a food processor.

Add ground sirloin and ground Italian sausage to the pot. Cook until fully cooked but not browned.

Fold in the minced vegetable mixture and cook until softened and fragrant.

Stir in tomato paste and allow it to cook for about 5 minutes.

Pour in red wine, scraping up any browned bits. Add milk, crushed tomatoes, bay leaves, and Parmesan rind. Season and reduce heat to low.

Cover and simmer the sauce on low heat for 2 ½ to 3 hours, stirring occasionally.

Cook pasta in salted boiling water until al dente, then drain without rinsing.

Rewarm the Bolognese sauce in a skillet. Toss in the cooked pasta, adding reserved pasta water as needed. Optional: add heavy cream.

Simmer combined pasta and sauce for 1-2 minutes. Plate and sprinkle with freshly grated Parmesan cheese before serving.