Preheat the oven to 325°F. Spray a 9 x 13 inch baking dish with cooking spray.
In a mixing bowl, mix together the frozen hash browns, cream of onion soup, sour cream, buttermilk dressing mix and chopped green onions. Season with black pepper to taste.
Stir everything until the ingredients are evenly distributed.
Add 4 tablespoons of melted butter and 1 1/2 cups of shredded white cheddar cheese. Mix well.
Pour the mixture into the baking dish and drizzle with the remaining 2 tablespoons of melted butter.
Sprinkle 1/2 cup of cheese on top then spread the crushed ranch flavored potato chips evenly over it all.
Bake for 1 hour and 20-25 minutes until golden and bubbly.