Add onion, and cook until translucent, stirring as needed.
In a large bowl, stir together sour cream, cream of chicken soup, salt, pepper, dry mustard, and 2 cups of cheddar cheese.
Add hash browns and onions, and toss to combine.
Grease a 9x13-inch baking dish.
Add hash brown mixture to prepared baking dish.
Bake for 45 minutes.
Sprinkle with remaining 1/2 cup cheese.
Continue baking for 5-10 minutes, or until cheese is melted.
Video
[adthrive-in-post-video-player video-id="1uaA7xsD" upload-date="2019-03-16T02:49:28.000Z" name="FUNERAL POTATOES " description="Funeral potatoes (cheesy potatoes) are a quick and easy side dish made with hashbrown potatoes. "]
Notes
Sour cream: I've used both lite sour cream and plain, non-fat Greek yogurt. Both work well as substitutions for regular sour cream. I don't recommend using fat-free sour cream in this recipe.
Cream of chicken soup: Either regular or 98% fat-free cream of chicken soup will work.
Corn flake topping: You can add a cornflake topping for some crunch. Sprinkle the remaining 1/2 cup cheese over the top of the unbaked casserole. Add 2 cups of cornflakes over the top of the unbaked casserole. Drizzle 2 tablespoons of melted butter over the cornflakes. Bake as directed.
Make ahead: This casserole can be made through step 7, covered, and chilled for up to 24 hours prior to baking. When you're ready to bake it, set the casserole out while the oven preheats. You may find that you need to increase the cooking time depending on how cold the casserole is.