Preheat oven to 375°F (190°C). Grease a 9x13-inch baking dish.
Sauté vegetables – In a skillet, melt butter over medium heat. Add chopped celery and onion, sautéing until soft (about 5 minutes).
Mix the base – In a large mixing bowl, combine shredded chicken, crumbled cornbread, and sautéed veggies.
Season & moisten – Stir in salt, pepper, poultry seasoning, and sage. Slowly pour in chicken broth while mixing. Add beaten eggs and mix until fully incorporated.
Bake – Transfer the mixture to the prepared baking dish and spread evenly. Bake uncovered for 40-45 minutes or until golden brown and set.
Rest & serve – Let it rest for 10 minutes before serving. Enjoy warm!