Celery and Apple Stuffing

Name: Celery and Apple Stuffing
Yield: Serves 8 – 10
Ingredients: 2 tbsp minced fresh sage; Salt; 5 outer celery ribs, cut lengthwise into thirds, then diced crosswise; 1 tbsp each minced fresh rosemary and thyme; 1 small yellow onion, chopped; ½ cup (4 oz/125 g) unsalted butter, plus more for the baking dish; 1 lb (500 g) stale coarse country white bread or focaccia, torn into 1-inch (2.5-cm) chunks; 1 large Golden Delicious or Granny Smith apple, about ½ lb (250 g), halved, cored, and diced; ¼ cup (⅓ oz/10 g) finely chopped fresh flat-leaf parsley leaves; About 3 cups (24 fl oz/750 ml) low-sodium vegetable or chicken broth; 1 cup (4 oz/125 g) jarred peeled chestnuts, chopped