Preheat oven to 350°F (175°C).

Thaw frozen hash browns.

Melt 1/2 cup of butter.

Chop the onion.

In a large bowl, combine thawed hash browns, melted butter (1/2 cup), chopped onion, chicken soup, sour cream, and shredded Cheddar cheese.

Stir all ingredients together until well combined.

Grease a 2 1/2-quart casserole dish.

Spoon the potato mixture into the prepared casserole dish, spreading evenly.

Crush the corn flakes into small pieces.

Melt the remaining 1/4 cup of butter.

Combine the crushed corn flakes and melted butter (1/4 cup).

Sprinkle the corn flake mixture evenly over the potato mixture in the casserole dish.

Bake in the preheated oven for 50 minutes, or until golden brown and bubbly.

Let cool slightly before serving.