Step 1: Preheat and Sauté

1. Preheat your oven to 375°F (190°C).
2. In a skillet, melt 2 tablespoons of butter over medium-high heat.
3. Add the chopped onions and celery, sautéing until softened and fragrant (about 5 minutes).

Step 2: Mix the Ingredients

1. In a large bowl, combine cornbread (or dried bread), shredded chicken, sautéed vegetables, dried sage, poultry seasoning, cream of onion soup, and 1 cup of chicken broth.
2. Mix thoroughly until evenly combined.
3. Grease a 9×13-inch baking dish and spread the mixture evenly into the dish.

Step 3: Bake

1. Bake for 45 minutes or until the top is golden brown and the casserole is cooked through.

Step 4: Prepare the Gravy

1. In a skillet, melt ¼ cup unsalted butter over medium heat.
2. Whisk in ¼ cup of flour to create a roux, cooking until it lightly browns.
3. Gradually add the remaining chicken broth while whisking continuously.
4. Season with salt and pepper, then simmer until the gravy thickens.
5. Stir in the heavy cream and simmer for another 5-10 minutes.

Step 5: Serve and Garnish

1. Once the casserole is done, drizzle the creamy gravy over the top.
2. Garnish with chopped parsley or green onions for added color and freshness.
3. Serve hot and enjoy!