Begin by gently washing and draining the mushrooms or carefully wiping them clean. Arrange the mushrooms in a baking dish, ensuring that the stems are facing upwards. Place a small pat of butter on top of each mushroom, generously season with salt and pepper, and cover the dish with foil that has been lightly greased to prevent sticking. Proceed to bake the mushrooms in a preheated oven set to 375°F (190°C) for approximately 15 to 30 minutes, or until they are fully cooked to your desired tenderness.