- 1 loaf best-quality white bread (1 pound), crust on, cut into 3/4-inch cubes
- 1 celery root (about 2 pounds), peeled and cut into 1/2-inch pieces
- 1 tablespoon extra-virgin olive oil
- Coarse salt and freshly ground pepper
- 6 ounces (11/2 sticks) unsalted butter, plus more for baking dish
- 2 garlic cloves, finely chopped
- 3 large leeks, white and pale-green parts only, thinly sliced and rinsed well
- 3 tablespoons finely chopped fresh sage
- 3/4 cup chopped fresh flat-leaf parsley
- 5 cups homemade or store-bought low-sodium turkey or chicken stock
- 5 1/4 ounces toasted walnuts, coarsely chopped (1 1/2 cups)
- Arrange bread in a single layer on a baking sheet, and let stand, uncovered, at room temperature overnight. (Alternatively, bake bread in a 300-degree oven until dry but not browned, about 15 minutes.)
- Preheat oven to 425 degrees. Toss celery root and oil in a medium bowl. Season with salt and pepper. Arrange in a single layer on a rimmed baking sheet, and roast, stirring once, until celery root is tender and edges are golden brown, about 40 minutes.
- Melt 1 stick butter in a medium saucepan over medium heat. Add garlic and leeks, and cook, stirring often, until soft, about 8 minutes. Add the celery root, sage, parsley, and 4 cups stock, stirring to combine. Season with salt and pepper. Remove from heat.
- Toss bread with vegetable mixture in a large bowl. Fold in walnuts. Season with salt and pepper.
- To cook stuffing in a turkey: Stuff as directed (see Roast Dry-Brined Turkey recipe); for the remaining stuffing, stir in remaining 1 cup stock, spoon into a buttered 9-by-13-inch baking dish, and dot with remaining 1/2 stick butter. Cover with parchment, then foil, and bake in a 375-degree oven for 25 minutes. Uncover, and continue to bake until golden brown, 15 to 20 minutes. To bake all of the stuffing outside a turkey: Prepare and bake as directed above in a buttered 9-by-13-inch baking dish.
Make-Ahead Tip: Cut the bread into cubes and let dry overnight. If baking stuffing outside the bird, prepare components the day before, cover, and refrigerate. Assemble and bake just before serving.