In a large saucepan heated to medium heat, cook the pancetta for 5 minutes with butter and olive oil.
Add garlic, onion, carrots, celery, and bay leaves.
Let it cook and soften for 15 minutes, stirring occasionally.
Add the ground meats, then cook and brown for 10 minutes, stirring constantly.
Add the chopped liver and cook for 3 more minutes.
Pour in the wine and let it boil and evaporate for 10 minutes.
Add the tomato paste and nutmeg. Season well.
Add the chicken broth, cover, and let it simmer for 1.5 hours, stirring occasionally.
Remove the lid and cook for 30 more minutes.
Meanwhile, cook the pappardelle al dente.
Drain and serve with the sauce, grated parmesan, and a drizzle of olive oil.