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

Peel and cube the potatoes, then parboil them in salted water for 8-10 minutes until just tender.

In a mixing bowl, combine sour cream, cream of mushroom soup, French onion soup mix, and melted butter. Mix in drained pineapple and shredded cheese.

Fold the parboiled potatoes into the creamy sauce mixture and transfer to the prepared baking dish.

Optionally, sprinkle remaining cheese and breadcrumbs on top, then bake uncovered for 40-45 minutes until golden brown.

Let the dish rest for about 5 minutes before serving.