Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan.

Melt 2 tablespoons of butter in a skillet, add the diced onion, and sauté for about 5-7 minutes.

In a mixing bowl, combine the sautéed onions, garlic powder, cream of chicken soup, French onion dip, salt, and black pepper.

Fold in the frozen hashbrowns until evenly coated, then transfer to the greased baking pan.

Sprinkle the shredded sharp cheddar cheese over the hashbrown mixture.

Melt the remaining 4 tablespoons of butter and mix with crushed cornflakes, then spread evenly over the cheese.

Bake in the preheated oven for 50-60 minutes, until the cheese bubbles and the topping is golden brown.

Let the casserole rest for about 5 minutes before serving.