Preheat the oven. Set it to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
Prep the chicken. Pat the chicken dry. Cut into large bite-size pieces or leave breasts whole if you prefer slices after baking.
Season lightly with salt and pepper if using.
Make the creamy base. In a bowl, stir together the cream of chicken soup and sour cream until smooth. If you like, add a pinch of garlic powder or paprika for extra flavor.
Assemble the casserole. Spread a thin layer (2–3 tablespoons) of the creamy mixture on the bottom of the dish. Add the chicken in an even layer.
Spoon the remaining mixture over the top and smooth it out so all chicken is covered.
Add the topping. Crush the buttery crackers into coarse crumbs. Sprinkle evenly over the top to form a generous crust.
Cover and bake. Cover the dish tightly with foil and bake for 25 minutes. This helps the chicken cook gently and stay moist.
Uncover and finish. Remove the foil and bake another 15–20 minutes, until the topping is golden and the chicken is cooked through. Target temp: 165°F (74°C) in the thickest piece.
Rest, then serve. Let the casserole rest 5–10 minutes so the sauce thickens slightly.
Serve warm with a simple green salad, steamed veggies, or rice.