Preheat oven to 325. Peel and dice potatoes. Melt 1/2 C. butter. Cool, pour into plastic bag. Add potatoes, bread crumbs and onion. Shake until potatoes are evenly coated. Line a 10x14 pan with foil. Pour potatoes evenly into pan. Dot with remaining 1/4 C. butter over potatoes. Sprinkle with parmesan cheese, salt and pepper. Bake, uncovered until potatoes are soft.