Dottie's Potato Casserole

Ingredients

• 2 pound bag frozen hash browns, thawed
• 1/2 cup margarine, melted
• 1 teaspoon salt
• 1 teaspoon black pepper
• 1, 16 ounce container sour cream
• 1 can cream of celery soup
• 1/2 cup onion, chopped
• 2 cups Cheddar cheese, shredded
• 1 cup cornflakes, crushed
• 1/2 stick margarine