Preheat oven to 350ºF
Grease a 9 x 12 casserole dish with the butter.
Toast cornbread: Line a baking sheet with parchment paper. Spread cornbread cubes out evenly. Place cornbread in the oven to toast for approximately 10-20 minutes or until no longer soft, tips are turning brown & cubes are well toasted. Remove from oven and set aside.
Put sausage meat in a 9-inch cast-iron skillet & cook over medium heat. After a minute or so, add chopped sage and cook, breaking up lumps, until meat is about halfway cooked, about 3-5 minutes.
Add 1 TBS butter, onions, celery, mushrooms and garlic to the partially cooked sausage. Cook, stirring until softened and the sausage is cooked through - about 5 more minutes.
In a small bowl, combine broth and the egg & whisk to combine.
In a large bowl, add cornbread, cooked sausage mixture, pecans, salt, pepper, & parsley. Mix together with a big spoon until combined. Pour into the greased casserole dish. Pour the broth/egg mixture over the stuffing until it is just dampened, but not swimming in egg/broth mixture. Cover with foil and bake for approximately 20 minutes, until heated through & set.
Uncover stuffing and cook for additional 5-15 minutes or until the stuffing is golden brown on top.