Set your oven to preheat at 375°F (about 190°C). This ensures that it reaches the correct temperature by the time you're ready to bake. Next, lightly coat a 13x9-inch casserole dish with cooking spray to prevent sticking and make cleanup easier. Ensure the spray is evenly distributed across the bottom and sides of the dish for best results.
In a large bowl, combine the cream of chicken soup, sour cream, onion powder, garlic powder, salt, and pepper until well mixed. This step ensures all flavors are evenly distributed. Make sure to stir thoroughly so there are no lumps in your mixture. Next, gently fold in the cooked chicken pieces and 1 1/2 cups of cheese. Be careful not to overmix as this can make the mixture watery.
In a medium-sized mixing bowl, combine the crushed crackers and melted butter until well blended. This creates a flavorful crumbly topping that will add texture to your casserole. Ensure all pieces of butter are fully incorporated for an even distribution of flavor. The mixture should be moist enough to hold together when pressed but not too wet.
Sprinkle the cracker and butter mixture evenly over the chicken layer in your baking dish, pressing down gently to ensure it adheres well. Then, sprinkle the remaining ½ cup of cheese on top for a gooey finish. This step ensures that both the crackers and cheese will bake properly, creating a delicious topping that complements the chicken.
Place your chicken casserole in the preheated oven and bake for 35 to 40 minutes, or until the filling is bubbling and the crackers are lightly browned. Keep an eye on it towards the end of the baking time to ensure the crackers don't burn. The filling should be hot and bubbly throughout, indicating that the casserole has set properly.
Once baked, remove the casserole from the oven and let it cool for 15 to 20 minutes before serving. This cooling period allows the flavors to meld together and the filling to thicken slightly, ensuring a more cohesive texture when you cut into it. Skipping this step can result in a runny or undercooked center.