This honeynut squash, leek, and brie gratin is a delicious and comforting side dish that combines the sweetness of honeynut squash with the creaminess of brie cheese. The leeks add a subtle onion flavor, while the breadcrumbs provide a crispy topping. It is a perfect accompaniment to roasted meats or as a vegetarian main dish. The gratin can be assembled in advance and baked just before serving.