In a large mixing bowl, combine cream of chicken soup, sour cream, melted butter, and season with salt and pepper.
Add the thawed hash browns, shredded cheddar cheese, and chopped onions (if using). Mix well until combined.
Transfer the mixture to a greased slow cooker.
Sprinkle crushed cornflakes or breadcrumbs on top, if desired.
Cook on low for 4-5 hours or on high for 2-3 hours, until bubbly and heated through.
Serve warm and enjoy!