Step 1

Preheat the oven to 300°F and set an oven rack in the middle position. Butter a 9x13-inch baking dish.

Step 2

Cut the challah into 1-inch cubes and spread in a single layer on a rimmed baking sheet. Bake for about 25 minutes, or until dry and lightly toasted. Set aside.

Step 3

Increase the oven temperature to 350°F.

Step 4

Melt the butter in a large sauté pan. Cook the onions over medium heat, stirring occasionally, until soft and translucent. Add the celery, mushrooms, herbs, salt, and pepper and cook until celery is slightly softened, about 5 minutes more.

Step 5

In a large bowl, combine the toasted bread cubes, onion/vegetable mixture, and chicken broth and toss well.

Step 6

Transfer the stuffing to the prepared baking dish. Cover the dish with buttered foil and refrigerate until ready to bake (up to overnight).

Step 7

Bake for 20 minutes. Remove the foil and continue baking until golden, about 25 minutes more. Serve immediately.

Step 8

Make-Ahead Instructions: This dish can be prepared (but not baked) up to 1 day ahead of time. Cover the dish with buttered foil and refrigerate. When ready to bake, preheat the oven to 350°F. Bake for 20 minutes. Remove the foil and continue baking until golden, about 25 minutes more. Serve immediately.

Step 9

Freezer-Friendly Instructions: This dish can be frozen after baking, tightly covered, for up to 3 months. Defrost it in the refrigerator overnight then reheat it, covered with foil, in a 325°F oven until hot.