Preheat the oven to 375°F (190°C).
Prepare the bread: Place the torn bread pieces in a large bowl and set it aside. You can do this step ahead of time if desired, allowing the bread to dry slightly.
Cook the chicken sausage: In a skillet or frying pan, cook the 1 pound of chicken sausage over medium heat until fully browned and cooked through. Break it up into crumbles as it cooks. Once done, remove the sausage from the pan and add it to the bowl with the bread, leaving the drippings in the pan.
Sauté the vegetables: In the same pan, add ½ cup butter, 1 diced yellow onion, 4 minced garlic cloves, 1 cup diced celery, 1 ¼ teaspoons poultry seasoning, a dash of white pepper, salt, and pepper to taste. Cook the mixture for 5-7 minutes, or until the vegetables become tender.
Combine everything: Pour the cooked vegetables and any remaining butter from the pan over the bread and sausage mixture. Gradually stir in 1 ½ cups chicken stock, mixing as you go. The stuffing should be moist but not soggy; if necessary, add more stock until no dry spots remain.
Transfer to a baking dish: Grease a 2 ½-quart casserole dish, and spread the stuffing mixture evenly into the dish.
Bake the stuffing: Bake in the preheated oven for 25-30 minutes, or until the top is slightly golden and crunchy.
Serve: Remove the stuffing from the oven, let it cool for a few minutes, and serve alongside your main dish.