Lightly grease the inside of your slow cooker with cooking spray or a little bit of butter.

In a large bowl, combine the frozen hash browns, cream of chicken soup, sour cream, melted butter, chopped onion, garlic powder, salt, and pepper. Mix everything together really well.

Stir in one cup of the shredded cheddar cheese. Reserve the other cup for later.

Pour the mixture into your prepared slow cooker. Spread it out into an even layer.

Cover and cook on low for 4-6 hours, or on high for 2-3 hours. The casserole is done when the potatoes are tender and the edges are starting to get a little golden brown.

During the last 30 minutes of cooking time, sprinkle the remaining cup of cheddar cheese over the top of the casserole.

If using cornflake or cracker topping, mix the crushed flakes/crackers with the melted butter and sprinkle it over the cheese.

Continue cooking, covered, for the remaining 30 minutes, or until the cheese is melted and bubbly and the topping is golden brown (if using).

Once it's done, turn off the slow cooker and let the casserole sit for about 10-15 minutes before serving.