Preheat the oven to 350 degrees F and spray a 9x13 baking dish or casserole dish with nonstick cooking spray.
In a large mixing bowl, combine 32 ounces thawed shredded hash browns, ½ cup melted butter, 1 can cream of chicken soup, 16 ounces sour cream, ½ finely chopped white onion, 1½ cups shredded cheddar cheese, 1 teaspoon salt, and ½ teaspoon black pepper.
Stir the mixture thoroughly until all ingredients are evenly combined.
Spread the mixture evenly into the prepared baking dish.
Bake for 40–45 minutes until the casserole is heated through and the top begins to brown slightly.
Remove the casserole from the oven and sprinkle the remaining ½ cup shredded cheddar cheese evenly on top.
Return the casserole to the oven and bake for an additional 3–5 minutes until the cheese is melted.
Allow the casserole to cool at room temperature for 10–15 minutes.
Top with chopped fresh parsley before serving and enjoy!
Notes
It is very important to thaw the hash browns before making this casserole. Refrigerate the leftover casserole in an airtight container for up to 5 days. This casserole can be prepped the night before. Refrigerate and let the casserole come to room temperature before baking.