To dry the bread cubes, spread them on two rimmed baking sheets; leave them out (uncovered) overnight, or bake in a 300-degree oven for about 30 minutes.
- 4 tablespoons butter, plus more for baking dish
- 2 large onions, cut into 3/4-inch dice
- 6 stalks celery, sliced crosswise 1/4 inch thick
- Coarse salt and ground pepper
- 1 1/2 pounds assorted mushrooms, trimmed and halved or quartered (for uniform pieces)
- 2 loaves Italian bread (1 pound total), cut into 1-inch cubes (about 16 cups) and dried
- 1 can (14.5 ounces) reduced-sodium chicken or vegetable broth
- 1 cup coarsely chopped fresh parsley
- 3 large eggs, lightly beaten
Preheat oven to 400 degrees. Butter an 8-inch square (or other shallow 2-quart) baking dish for extra stuffing.
Heat butter in a large skillet over medium heat; add onions, celery, 1 1/2 teaspoons salt, and 1/4 teaspoon pepper. Cook, tossing often, until beginning to brown, 12 to 15 minutes.
Add mushrooms. Cover; cook until they release liquid, 5 to 7 minutes. Uncover; cook, tossing occasionally, until tender and liquid has evaporated, 10 to 12 minutes more. Transfer to a large bowl; let cool completely.
Add bread, broth, parsley, and 3/4 cup water to bowl; toss well. Season with salt and pepper; mix in eggs.
Prepare and stuff turkey. Transfer extra stuffing to prepared baking dish, and cover with buttered foil. Refrigerate until ready to cook.
During last 20 minutes of turkey roasting time, put covered dish in oven. Bake 25 minutes. Remove foil; bake until golden, 20 to 25 minutes.