2 loaves good-quality white bread, cut into 3/4-inch cubes (about 20 cups)
1 1/2 pounds fresh chestnuts (4 cups), scored with an X
3/4 cup unsalted butter (1 1/2 sticks)
4 small onions, peeled and cut into 1/4-inch dice (about 3 cups)
1 bunch celery, cut into 1/4-inch dice (about 4 cups)
3 tablespoons finely chopped fresh sage
5 cups homemade or low-sodium store-bought chicken stock
1 tablespoon coarse salt
3 cups coarsely chopped fresh flat-leaf parsley
Freshly ground pepper
1. Spread bread cubes in single layers on baking sheets. Let dry at room temperature, uncovered, overnight.
2. Bring a medium saucepan of water to a boil. Add chestnuts; cook until soft, about 20 minutes. Drain; let cool slightly. Peel and quarter chestnuts; set aside. Peeled chestnuts can be refrigerated in an airtight container 2 to 3 days.
3. Melt butter in a large skillet over medium heat. Add onions and celery; cook, stirring, until onions are translucent, about 10 minutes. Add sage; cook 3 minutes. Stir in 1/2 cup stock; cook until reduced by half, about 5 minutes.
4. Transfer onion mixture to a large bowl. Add remaining 4 1/2 cups stock, the chestnuts, bread, salt, and parsley; season with pepper. Toss to combine. If not stuffing turkey, transfer to a buttered 17-by-12-inch baking dish. Cover; bake at 350 degrees for 25 minutes. Uncover; bake until hot and golden brown, 30 minutes more.