Preheat oven to 375 degrees.
Caramelize diced onion over medium heat for 20 minutes in olive oil or butter.
To a large mixing bowl add thawed potatoes, caramelized onions, cream of chicken soup, sour cream, shredded cheese, salt and pepper. Mix until combined.
Add potatoes to a buttered 9x13 dish.
Bake uncovered at 375 for one hour. Broil for additional color with the lid open.
Cool for at least 10 minutes before serving.