Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish with butter or cooking spray.

Peel and cube the potatoes. Parboil them in salted water for 8-10 minutes until tender. Drain and let cool.

In a large mixing bowl, combine sour cream, cream of mushroom soup, and French onion soup mix. Add melted butter and stir to mix well. Fold in pineapple and shredded cheese.

Fold in the parboiled potatoes until thoroughly coated. Pour mixture into the baking dish and spread evenly.

Sprinkle additional cheese and optional breadcrumbs on top. Bake uncovered for 40-45 minutes or until bubbly and golden brown.

Allow to cool for 5 minutes before slicing and serving.