Prepare the Base Mixture: In a large mixing bowl, combine the uncooked rice, chicken broth, milk, cream of mushroom soup, and cream of chicken soup. Whisk until the mixture becomes creamy and well blended. Stir in the onion, peas and carrots, garlic powder, onion powder, salt, and pepper. The mixture should look rich and slightly soupy — this helps the rice cook perfectly in the oven.

Add the Chicken: Fold in the cooked, shredded chicken, mixing until it’s evenly distributed throughout the creamy base. You can use rotisserie chicken for convenience or leftover baked chicken for added flavor. Make sure every grain of rice is coated in the sauce for even cooking.

Assemble the Casserole: Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with melted butter or nonstick spray. Pour the mixture into the dish and spread it evenly with a spatula. Drizzle the remaining melted butter over the top — this helps the surface turn golden and adds a touch of richness.

Bake to Perfection: Cover the casserole tightly with foil to keep the moisture in and bake for 45 minutes. Remove the foil and sprinkle cheddar cheese evenly on top (if using). Continue baking uncovered for another 15 minutes, or until the rice is tender and the cheese is melted and bubbly. The top should have a light golden crust, and the edges should be slightly crisp.

Rest and Serve: Once baked, remove the casserole from the oven and let it rest for about 10 minutes before serving. This allows the sauce to thicken slightly and the flavors to meld together beautifully. Garnish with fresh parsley for a pop of color and freshness.