Preheat oven to 350 degrees (if roasting a turkey, the oven can be at 325 degrees, just add a few extra minutes to your cooking time) Spray a casserole dish with non-stick spray.
Pour stuffing cubes into a large bowl.
Heat chicken broth in a small saucepan till warmed, keep on low till needed.
Brown and crumble the sausage in a medium frying pan, drain, and set aside.
Melt the butter in a large frying pan over med-high heat. Add the celery, onion, carrots, mushrooms, and garlic. Saute till just about softened.
Add poultry seasoning, Italian seasoning, and salt and pepper to taste.
Add in the sausage and the fresh parsley; combine. Heat till the sausage is warmed again.
Pour the sausage/vegetable mixture over the stuffing cubes and combine well. Once it's combined, start to add the chicken broth, a little at a time. You want your stuffing to be moist, not mushy. You'll know when it's enough. You may not use all of the broth you warmed up.
At this point, you can spoon it into the casserole dish you prepared and bake in a 350-degree oven for about 30 - 45 minutes, till the top is golden brown and the stuffing is hot. - OR - If you are stuffing a turkey, do this when you are ready to put the bird in the oven and not a moment before. As I mentioned above, this will stuff your bird and also a casserole dish too.