Instructions

• Preheat oven to 350°F. Butter a 9×13-inch baking dish and set it aside. Make sure the hash brown potatoes are mostly thawed and drain any excess water.
• In a medium bowl, stir together the 16 ounces sour cream, the 10.5-ounce can of cream of chicken, 1/2 cup of the melted butter, the 1/4 cup thinly sliced green onions (or 1 tablespoon minced onions, if using), 1/2 teaspoon Kosher salt, and 1/4 teaspoon ground black pepper until evenly combined.
• Add the 32 ounces thawed diced hash brown potatoes and 1 1/2 cups shredded cheddar cheese to the bowl. Fold gently until the potatoes and cheese are evenly coated with the sauce.
• Spread the potato mixture into the prepared 9×13-inch baking dish in an even layer. If you want extra cheese, sprinkle more shredded cheddar over the top now.
• Place 2 cups cornflakes in a zip-top bag and crush them to coarse crumbs with a rolling pin (or crush in a bowl with a spoon). Pour the crushed cornflakes into a small bowl, add the remaining 1/4 cup melted butter, and stir until the flakes are evenly coated.
• Evenly sprinkle the buttered cornflake crumbs over the top of the casserole.
• Bake uncovered for 40 to 45 minutes, or until the topping is golden brown and the casserole is bubbly around the edges.
• Remove from the oven and let rest 5 minutes before serving.