Sausage - In a very large pot, I usually use my big dutch oven for this or you can use 2 large sauce pans and make this ahead and just refrigerate over night. One less thing to do on Turkey Day.
Add 2 tablespoons butter and melt on medium heat. Add in the sausage and slowly brown.
Vegetables - Then in the same pan with the sausage, melt the remaining butter on medium to medium low heat, then add in the onions, celery, mushrooms, nuts and cook 10-15 minutes, just slowly, don't rush them. Add in the seasoning and mix well.
Bread - In a small bowl, add the milk and soak the fresh bread slices and then squeeze out most of the milk. Then break up the fresh bread into crumbs until you have 3 cups. Add the fresh bread crumbs to a large bowl, along with the cornbread and herb stuffing cubes. Mix to combine.
Then add in the sausage and vegetable mix and 3 cups of chicken broth and once again, mix well. Add a little at a time until you get a nice moist stuffing. Check for seasoning, and add more salt and pepper if needed.
Stuff the turkey right away if making it that day and then the remaining stuffing put in a baking dish sprayed with a non stick spray. Cover with foil and refrigerate until turkey day. You can also put both in the refrigerator until the next day as well.
Bake - Make sure to take the stuffing out of the refrigerator for 30 minutes at least before baking to take the chill off. I check the stuffing for moisture before I bake and often add an additional 1 cup or more of the chicken stock to ensure moist stuffing. Especially for the stuffing out of the bird. The stuffing in the bird will get moisture from the turkey.
Keep covered with foil and bake 30-45 minutes until heated through (my oven is usually on 350-375.