Slow Cooker Potato Casserole

cream of chicken soup

sour cream (I used light)

small onion, finely chopped

butter, melted

salt

pepper

shredded cheddar cheese, divided

pkg frozen cubed hash brown potatoes , thawed (however, I recommend keeping them frozen if you want the potatoes more chunky and not so mushy)

diced green onion or chives, optional for garnish