Next, adjust your oven temperature to 400°F (205°C) to prepare your mushroom topping. In a skillet, combine your assortment of mushrooms—such as oyster, cremini, shiitake, and black oyster—with fresh thyme leaves. Sauté them until tender and aromatic, allowing the mushrooms to soften and release their moisture. Pour in the balsamic vinegar, sea salt, ground pepper, and lemon juice. Stir frequently, cooking until the mushrooms absorb the flavors, becoming tender and lightly caramelized.