Heat the oven to 225 F.

Cut the bread into 1/2-inch cubes and spread it out in a single layer on a lightly oiled large baking sheet. Bake until dry and lightly toasted, about 40 to 50 minutes. Note: You can do this ahead of time —let the toasted bread cubes cool and put them in a food storage bag until you're ready to make the stuffing.

Lightly grease a 3-quart baking dish or spray it with cooking spray, and heat the oven to 350 F.

Melt the butter in a large saucepan or Dutch oven over medium heat. Add the onions, celery, and carrots, if using. Cook the vegetables, stirring frequently, for about 5 minutes, until the onions are translucent.

Combine the bread cubes with the sautéed vegetables, parsley, sage, rosemary, thyme, salt, and pepper. Add 2 1/2 cups of chicken stock. Add more, as needed. Taste and adjust the seasonings.

Whisk the eggs in a separate bowl until well blended and add them to the bread mixture. Stir to combine thoroughly.

Transfer the stuffing mixture to the prepared baking dish and bake until lightly browned, about 45 to 55 minutes.