To Make the Bread Cubes: Preheat the oven to 250°. Butter or spray a baking dish or sheet pan and set aside. Scatter bread in a single layer; bake, stirring occasionally, until dry, about 45 minutes to 1 hour. Let cool; transfer to a very large bowl. Or let sit on the counter overnight.

Preheat the oven to 350° and butter a 3-quart casserole or baking dish. Set aside.

To Make the Stuffing: Melt the butter in a large skillet over medium-high heat; add onions and celery. Cook and stir until the vegetables begin to brown, about 8 to 10 minutes. Then add to the bowl with the dry bread cubes. Stir in the herbs, salt and pepper into the bread and vegetable mixture. In a small bowl, whisk together the broth and egg. Pour over the stuffing mixture and gently fold to combine. Transfer the stuffing to the prepared baking dish, cover with foil, and bake until an instant-read thermometer, inserted into the center of the stuffing registers 160°F, about 35 to 40 minutes. Uncover and bake another 5 minutes or until the top is a little toasty.