Grease a 9 x 13-inch baking dish. Preheat the oven to 325 degrees.
In a large mixing bowl, combine the cream of chicken soup, sour cream, cheddar cheese, and onion. Mix well. Season to taste with salt and pepper. Stir in potatoes. Spoon this mixture into the prepared baking dish.
In a small mixing bowl, combine crushed cornflakes and melted butter. Sprinkle over the potato mixture.
Bake for 2 hours at 325 degrees.
Notes
If you prefer saucier potatoes, use 2 more cups of cream of chicken soup.Promptly store leftovers in an airtight container in the refrigerator, for up to 3 days.Freezing instructions: Simply wrap well and freeze for 4 to 6 weeks. To serve: bake according to directions.To make this gluten-free: I have tested this using Bob's Red Mill 1 to 1 Baking Flour in the cream soup and gluten-free breadcrumbs in the topping. Everyone enjoyed it, gluten-eaters and those who eat gluten-free. You can also purchase a gluten-free cream of chicken soup at the store.