Directions

1. 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.)
2. 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.
3. 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.
4. Toss bread with vegetable mixture in a large bowl. Fold in walnuts. Season with salt and pepper.
5. 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.