In a medium skillet heat 1 tablespoon butter and cook your onion until soft (about 5 mins)In a large mixing bowl combine your hash browns, salt, black pepper, chives, sour cream, shredded cheddar cheese, cream of chicken soup and your cooked onion. Stir well. It may take some serious arm muscle to work this all together if your hash browns are still frozen but should mix easily if thawed.Preheat your oven to 375°. Put your potato mixture into a 9x13 casserole dish and cook in the oven for 30 minutes. Take out and stir the whole casserole well. Put back in the oven and continue to cook until it's bubbling on the sides and in the middle, about 20-30 more minutes depending on your oven. Once it's bubbling in the middle you know it's done.Take the casserole out of the oven and sprinkle your crushed onion and Dorito mixture on the top. Put back in the oven for an additional 5 minutes but watch carefully so the topping doesn't burn.Remove from the oven and serve immediately.