Heat oven to 350°F. Grease a 9x13-inch baking dish.
Break up the hash browns so they’re loose and no longer icy.
Whisk soup, sour cream, 6 tbsp melted butter, onion, salt, pepper, garlic powder, and paprika in a large bowl.
Stir in 1.75 cups of the cheddar until combined.
Fold in the hash browns until evenly coated. Spread the mixture in the prepared dish.
Mix crushed cornflakes with the remaining 2 tbsp melted butter. Sprinkle over the casserole, then top with the remaining 0.5 cup cheddar.
Bake 45–50 minutes until bubbly and deep golden. Rest 10 minutes, then finish with chives and serve.