Preheat the oven: Set your oven to 350°F. In a large baking dish, combine the chopped onion, carrots, celery, wild rice, and chicken broth. Cover tightly with foil and bake for 1 hour and 15 minutes.

Prepare the sauce: While the rice is cooking, melt 4 tablespoons of butter in a saucepan over medium heat. Add the flour, salt, and poultry seasoning. Cook for 1 minute. Gradually whisk in the milk to form a smooth, creamy sauce.

Optional topping: Melt the remaining 6 tablespoons of butter. Toss with the cubed bread. (If you prefer a casserole without the topping, you can skip this step.)

Assemble the casserole: Once the rice is cooked, remove the foil. Add the raw chicken pieces and the creamy sauce to the dish. Stir everything together to combine. Arrange the buttered bread cubes evenly on top.

Bake: Increase the oven temperature to 450°F. Bake uncovered for an additional 20-30 minutes until the chicken is fully cooked (no longer pink) and the bread cubes are golden brown.

Serve: Once baked, garnish with salt, pepper, or parsley for a fresh pop of flavor and color. Enjoy!