Preheat the Oven: Set your oven to 350°F (175°C).
Assemble the Base: In a 13x9-inch baking dish, combine the sliced onion, French onion soup, chicken broth, and rinsed rice. Stir to ensure everything is evenly distributed.
Add Butter and Chicken: Place the butter slices evenly over the rice mixture. Lay the chicken pieces on top of the butter and rice.
Top with Cheese and Seasoning: Sprinkle the shredded cheese over the chicken, followed by the onion soup mix.
Bake Covered: Cover the baking dish tightly with aluminum foil. Bake in the preheated oven for 1 hour and 15 minutes.
Add Crispy Onions: After the initial baking time, remove the foil and evenly distribute the crispy fried onions on top. Return the dish to the oven and bake, uncovered, for an additional 15 minutes, or until the onions are golden and the rice is tender.
Serve: Let the casserole rest for a few minutes before serving. Enjoy warm