Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.
Stir Cheddar cheese, hash brown potatoes, sour cream, cream of chicken soup, onion, and 1/2 cup melted butter together in a large bowl. Pour into prepared baking dish.
Bake in the preheated oven for 45 minutes. Stir crushed chips and 1/2 cup melted butter together in a bowl; spread over hash browns mixture. Bake until casserole is bubbling and topping is golden, about 15 minutes more.