Please diced potatoes in a 9″ x 13″ baking dish. Heat soup, butter, sour cream and onions in a small pot, stir until all are well combined. Cover potatoes with the liquid and then cover with the bread crumbs and parmesan cheese mixture. Bake at 350 degrees for 15 minutes, then add the cheddar cheese to the top and finish baking for another 30 minutes. Let cool for 5 – 10 minutes before serving.