You will need:
1 (2 lb) bags frozen hash browns, thawed
2 -3 green onions, chopped
1 small onion, chopped
2 cups grated cheddar cheese ( more to top after baking if desired)
3/4 cup grated parmesan cheese, divided
2 teaspoons garlic powder
1 teaspoon ground black pepper ( or to taste)
1 teaspoon seasoning salt
1/3 cup melted butter
3/4 cup sour cream
3/4 cup milk
1 (10 ounce) cans undiluted cream of mushroom soup
Set oven to 350°F.
Butter a 13×9-inch casserole dish.
In a large bowl stir together the undiluted soup, milk, sour cream, melted butter, seasoned salt, black pepper, garlic powder and 1/4 cup Parmesan cheese; whisk or mix until well combined.
Mix in the cheddar cheese, onions and hash browns.
Spread into prepared baking dish.
Sprinkle with about 1/2 cup parmesan cheese.
Bake uncovered for 40 minutes or until hot and bubbly.
If desired sprinkle about 2 cups grated cheddar cheese on top and return to oven for 3 minutes to melt the cheese.