Preheat your oven to 350°F (175°C). Lightly grease a medium baking dish so the casserole doesn’t stick and cleans up easily later.
In a large bowl, combine the shredded chicken, cooked rice, frozen vegetables, and cream of chicken soup. This is the base that will become the cozy texture you’re after.
In a separate bowl, whisk together the sour cream, cream cheese, milk, garlic powder, onion powder, and a pinch of salt and pepper until smooth. This creates a creamy, luxurious sauce that clings to every bite.
Pour the creamy sauce over the chicken mixture and stir until everything is evenly coated. Fold in half of the shredded cheddar to start building the cheesy foundation.
Transfer the mixture to the prepared baking dish. Smooth the top so it bakes evenly. Pour a light splash of chicken broth around the edges if you notice the mixture looks dry; this helps keep the texture moist.
Sprinkle the remaining cheddar over the top. If you like a bit of crunch, sprinkle the French fried onions evenly on top.
Bake for 25–30 minutes, until the casserole is bubbling in the center and the cheese has melted into a glossy sheen. If you want extra browning on top, switch the oven to broil for the last 2–3 minutes—watch closely to avoid burning.
Let the dish rest for 5 minutes before serving. This helps the flavors settle and makes serving easier.