Prepare the Cornbread (If Needed)
Preheat the oven to 400°F (200°C).
In a mixing bowl, whisk together cornmeal, flour, baking powder, and salt.
Add eggs, buttermilk, and melted butter, then stir until combined.
Pour into a greased baking dish and bake for 20-25 minutes, until golden brown. Let cool, then crumble.
Cook the Chicken (If Not Using Rotisserie)
Place chicken breasts or thighs in a pot with water or broth.
Add salt, pepper, and a bay leaf (optional). Simmer for 20-25 minutes until fully cooked.
Remove, let cool, then shred with two forks.
Sauté the Vegetables
Melt 2 tablespoons of butter in a skillet over medium heat.
Add chopped onions and celery, sauté until soft and fragrant (about 5 minutes).
Mix the Dressing
In a large mixing bowl, combine crumbled cornbread, torn white bread, shredded chicken, and sautéed vegetables.
Gradually pour in chicken broth, stirring to moisten.
Add beaten eggs, melted butter, poultry seasoning, sage, black pepper, and salt. Mix well.
Bake the Dressing
Preheat the oven to 350°F (175°C).
Transfer the mixture into a greased 9x13-inch baking dish.
Bake uncovered for 40-45 minutes, until golden brown and slightly crispy on top.
Let rest for 5 minutes before serving.