Our Favorite Thanksgiving Stuffing with Sausage and Cornbread

Name: Our Favorite Thanksgiving Stuffing with Sausage and Cornbread
Ingredients: 1/2 cup (1 stick) unsalted butter, plus more for pan; 1/2 pound good-quality day-old crusty country-style or peasant bread, torn into 3/4 pieces (about 5 cups); 1/2 pound day-old cornbread, broken into 3/4 pieces (about 5 cups); 1 pound breakfast sausage links, casings removed, or ground breakfast sausage mix, broken up into 1/2 pieces; 2 1/2 cups chopped onions (about 1 medium plus 1 large onion); 3 medium celery stalks, sliced; 2 large eggs; 2 1/2 cups low-sodium chicken broth; 1/2 cup chopped parsley; 2 tablespoons chopped sage; 1 tablespoon chopped thyme; 2 teaspoons chopped rosemary; 2 teaspoons kosher salt; 1 teaspoon freshly ground black pepper; A 13x9x2 or other 3-quart baking dish