Crumble prepared cornbread into small pieces and preheat oven to 350 degrees.
In a large cast iron skillet, melt butter and sauté diced onions until softened.
Add in hot Italian sausage to the skillet and cook through; use a wooden spoon to break up the cooked sausage into small pieces.
Fold celery seed, chopped sage, and dried cranberries into the sausage mixture.
Pour the apple cider into the skillet to deglaze the pan, scraping up any bits stuck to the skillet; remove skillet from the heat.
Add the crumbled corn bread to the skillet and then stream in the warm chicken broth, mixing the ingredients together until combined.
Season to taste with salt and pepper, and then put the skillet in 350 degree oven for 20-25 minutes; garnish with fresh chopped leaves and serve immediately.
Note: To make ahead, prepare the dish up until the point of baking, cover and set aside, and then bake immediately before serving.