Toast the bread. Preheat oven to 350°F. Scatter torn bread pieces in a single layer on a rimmed baking sheet. Bake, stirring occasionally, until dried out and lightly golden, about 30-40 minutes. Let cool completely.
Grease the baking dish. Butter a 9x13-inch baking dish and set aside.
Cook the vegetables. Melt 3/4 cup butter in a large skillet over medium-high heat. Add chopped onions and sliced celery. Cook, stirring often, until vegetables are softened and just beginning to brown, about 10-12 minutes. Transfer to a large bowl and let cool.
Combine bread and herbs. Add the toasted bread pieces, parsley, sage, rosemary, thyme, salt, and pepper to the bowl with the cooled vegetables. Toss gently to combine.
Add first portion of stock. Drizzle 1 1/4 cups of chicken stock over the bread mixture. Fold gently to distribute evenly.
Make the egg mixture. In a measuring cup, whisk together the eggs and remaining 1 1/4 cups chicken stock until well combined.
Combine everything. Pour the egg mixture over the bread mixture. Fold gently but thoroughly until everything is evenly moistened and combined.
Transfer to baking dish. Transfer the stuffing mixture to the prepared baking dish, spreading it evenly. Cover with parchment paper, then top with aluminum foil.
Refrigerate until ready to use.
Remove from fridge at least one hour before baking.
Bake covered. Bake until an instant-read thermometer inserted into the center registers 160°F, about 40-50 minutes.
Finish uncovered. Remove the parchment and foil. Continue baking until the top is golden brown and crispy, about 35-45 minutes longer.
Rest and serve. Let the stuffing rest for 10 minutes before serving. This allows it to set up and makes it easier to scoop.
