Preheat oven to 350F.
In a medium or large pan, saute onions and (optional) celery in butter. Then add cooked, drained, crumbled sausage, Croutonz, and 1 cup of stock or broth. Toss well and let rest for 10 minutes, tossing occasionally.
Add ¾ cup broth or broth/egg mixture, poultry seasoning, salt and pepper, and any other desired add-ins. Add more stock if a moister stuffing is preferred.
Bake in a well-buttered casserole or skillet. For more crusty surface bits, use a larger one. Bake 20 to 30 minutes or until thoroughly heated and crusty, as desired.
Can make ahead, reheats well.