Grease your slow cooker with a light coating of butter or cooking spray to prevent sticking. While that's done, measure out all your ingredients and have them ready by the slow cooker. Shred your cheddar cheese from a block if you haven't already—freshly shredded cheese melts much more smoothly than pre-shredded varieties, which contain anti-caking agents that can make your casserole grainy.

In the greased slow cooker, combine the sour cream, condensed cream of chicken soup, and all the dry seasonings: onion powder, garlic powder, salt, pepper, and smoked paprika. Whisk these together until the seasonings are fully incorporated and the mixture is smooth with no lumps. This ensures the flavors distribute evenly throughout the casserole rather than settling on the bottom.

Add the frozen diced hashbrowns and freshly shredded cheddar cheese to the creamy sauce base from Step 2. Stir everything together until the potatoes are evenly coated and the cheese is distributed throughout. I like to fold rather than stir aggressively to keep the hashbrowns from breaking apart too much—you want some texture in the final dish.

Cover the slow cooker and cook on low for 3 to 4 hours. The casserole is done when the potatoes are tender and the sauce is bubbling gently around the edges. You don't need to stir during cooking—the gentle heat will cook everything evenly without the risk of the potatoes becoming mushy.

Give the casserole a good stir to redistribute the creamy sauce and break up any large chunks of potato that may have clumped together. The mixture should be smooth and creamy with tender potato pieces throughout. Top with fresh parsley for color and a fresh flavor contrast to the rich, savory casserole.