Preheat oven to 350 degrees. Mix together hash browns, 1/2 cup melted butter, onion soup, sour cream, chopped onion, cheddar cheese, salt, and pepper. Spread mixture in casserole dish. Saute 1/4 cup butter and crushed cornflakes in pan until just slightly browned then sprinkle over potato mixture. Bake uncovered at 350 degrees for 40 minutes.