Lentil and Mushroom Gratin is a hearty and flavorful vegetarian dish that combines the earthy flavors of lentils and mushrooms with a creamy and cheesy topping. This gratin is packed with protein and fiber from the lentils, and the mushrooms add a meaty texture. The dish is baked until golden and bubbly, creating a deliciously satisfying meal that is perfect for a cozy dinner or a holiday gathering.