12 cup day old bread cubes OR unseasoned bread cubes for stuffing
Melt butter in a large skillet over medium heat. Add mushrooms and celery. Cook for 2 to 3 minutes just until vegetables are tender. Add 2 cups chicken broth, parsley, minced onion, sage, poultry seasoning, salt and pepper. Reduce heat and simmer 10 minutes.
Place bread cubes in a large bowl. Pour the vegetable mixture over the bread cubes. Toss to combine. If dressing appears dry, add up to 1/2 cup chicken broth. Transfer to a 13 x 9-inch baking pan that has been sprayed with cooking spray. Bake at 350°F for 45 minutes or until dressing is well browned.