Mushrooms Au Gratin is a delicious and creamy side dish made with fresh mushrooms, cheese, and breadcrumbs. The mushrooms are sautéed until tender and then baked in a rich and cheesy sauce until golden and bubbly. This dish is perfect for mushroom lovers and makes a great addition to any meal. Serve it as a side dish with roasted meats or as a vegetarian main course with a side salad.