Pappardelle with White Bolognese

Ingredients

1 tablespoon olive oil
4 ounces pancetta (about 3/4 cup), finely chopped
9 medium-size fresh sage leaves, divided
1 cup cremini mushrooms (from 1 [8-ounce] package), finely chopped
1 cup yellow onion (from 1 small [7-ounce] onion), finely chopped
1/2 cup carrot (from 1 medium [3-ounce] carrot), finely chopped
1/4 cup celery (from 1 medium [1 1/2-ounce] celery stalk), finely chopped
3 garlic cloves, minced (about 2 teaspoons)
2 fresh bay leaves
1 teaspoon chopped fresh rosemary
1/2 teaspoon chopped fresh thyme
1 pound 85/15 lean ground beef
1 pound ground veal
2 cups dry white wine
2 cups lower-sodium chicken broth or beef broth
1/2 cup heavy whipping cream
1 teaspoon kosher salt, plus more to taste
1/2 teaspoon black pepper, plus more to taste
1/4 teaspoon ground nutmeg
1 (1-pound) package pappardelle pasta
1 ounce Parmigiano-Reggiano cheese (about 1/4 cup), grated, plus more for serving