01 - Set oven to 350°F (175°C); lightly grease a 9x13-inch baking dish.
02 - In a large mixing bowl, stir together cooked rice, shredded chicken, peas, and carrots until evenly distributed.
03 - In a separate bowl, whisk together condensed cream of chicken soup, sour cream, milk, half of the shredded cheddar cheese, garlic powder, onion powder, kosher salt, and black pepper.
04 - Pour the sauce mixture over the rice and chicken mixture; gently fold until combined. Transfer to the prepared baking dish and spread evenly.
05 - Sprinkle the remaining cheddar cheese evenly over the casserole surface.
06 - Toss the panko bread crumbs with melted butter and evenly distribute over the cheese layer.
07 - Bake uncovered for 25–30 minutes, or until bubbling at the edges and the topping is golden brown.
08 - Allow casserole to rest for 5 minutes before portioning and serving warm.