1 cup chopped onion (1 small or ½ of a large onion)
1 cup sliced fresh mushrooms
3 tablespoons butter
1 teaspoon The Old Mill Cornbread Dressing Seasoning, or salt and pepper to taste
3 to 4 cups shredded or chopped cooked chicken or turkey
2 cups chicken or turkey broth
1 cup sour cream
1 large egg
½ cup grated Parmesan cheese
Chopped fresh parsley, for garnish
Preheat the oven to 425 degrees F. For the cornbread, place the tablespoon of oil or bacon grease in a 10-inch cast iron skillet, and place the skillet in the oven to heat.
Place the cornmeal, egg, ¼ cup oil, and buttermilk in a large bowl and stir to just combine. When the skillet is hot, pour the batter into the skillet, and let it bake until golden, about 25 to 30 minutes. Remove the pan from the oven, and run a knife around the edges to loosen it. Turn it out onto a rack or board to cool. Set aside. Reduce the oven temperature to 350 degrees.
Place the celery, onion, and mushrooms in a large skillet with the butter over medium heat. When the butter melts and the vegetables begin to cook, reduce the heat slightly, and let the veggies cook until soft, about 4 to 5 minutes. Turn off the heat. Stir in the Cornbread Dressing Seasoning or salt and pepper to taste. Set aside.
When the cornbread is cool enough to handle, crumble it into pieces. Layer half of the cornbread in the bottom of a lightly greased 13- by 9-inch casserole. Top with half of the chicken or turkey, and half of the sautéed vegetables. Repeat with the rest of the cornbread, chicken, and veggies. Whisk together the chicken broth, sour cream, and egg. Pour the liquid over the top of the casserole. Cover the casserole with foil. Place the pan in the 350-degree oven.
Bake until the casserole has heated through, about 30 to 35 minutes. Remove the foil, and sprinkle the top with the Parmesan cheese. Turn the oven to broil, and place the casserole in the oven long enough for the top to brown, about 1 to 2 minutes. Garnish with chopped parsley, and serve.