Preheat oven to 350 degrees Fahrenheit.

In a large skillet over medium heat, melt 2 tablespoons of the butter. Add the onion and cook until soft, 3 to 5 minutes. Transfer the onions to a large mixing bowl.

Add 2 more tablespoons of butter to the hot skillet over medium heat and then stir in the apples and celery and cook for another 5 to 6 minutes, or until they are softened. Transfer the apples and celery to the mixing bowl with the onions.

In the same hot skillet, cook the sausage over medium heat until browned and cooked through, about 7 minutes, gently breaking it up into crumbles with a spatula as it cooks. Using a slotted spoon to drain off the excess grease, add the sausage to the mixing bowl with the onion mixture.

Add the cornbread and French bread pieces to the bowl, along with the beaten eggs, sage, parsley, and seasoning. Gently stir (or mix with your hands) until the mixture is evenly moist. Spoon it into a 9 x 13 glass baking dish.

Drizzle two cups of broth evenly over the cornbread mixture in the baking dish. Check to see if it is evenly moist. If all of the liquid is immediately sucked up by the bread and there are no juices in the dish, go ahead and add another cup of broth, 1/4 cup at a time - you don't want it to be soupy, but you do want it all to be very moist. Melt the last two tablespoons of butter and drizzle them over the top.

Bake uncovered for 40 to 50 minutes, or until the top is golden brown and the mixture is firm to touch. Cool for 5 minutes before serving.