In a saucepan combine onions, celery, butter, chicken stock, pepper and poultry seasoning. Bring to a boil, and cook for about 20 minutes, until the celery and onions are soft.
In a large skillet brown sausage. Drain and set aside.
Preheat oven to 350 degrees.
Place stuffing mix in a large bowl (I use a large pot I boil pasta in). Add cooked sausage. Add the chicken stock mixture in batches. Depending on the amount of bread crumbs, you may or may not need it all. Stir until the bread is moist, but not soggy. If you do not have enough liquid you can use a little milk.
Stir in walnuts if you are using them. Pour into a buttered 3 quart casserole pan. Cover and bake for 1 hour.
Remove from oven, and serve immediately