"Simple is Best" Dressing

INGREDIENTS

• 1 1/2 cups 1/4" slices celery
• 1 tablespoon chopped fresh thyme
• 2 large eggs
• 1 pound good-quality day-old white bread, torn into 1" pieces (about 10 cups)
• 2 1/2 cups chopped yellow onions
• 2 tablespoons chopped fresh sage
• 1/2 cup chopped flat-leaf parsley
• 1 tablespoon chopped fresh rosemary
• 1 teaspoon freshly ground black pepper
• 2 1/2 cups low-sodium chicken broth, divided
• 2 teaspoons kosher salt
• 3/4 cup (1 1/2 sticks) unsalted butter plus more for baking dish