Preheat the oven on 200°C.
Wash the mushrooms. Remove their stems and put them on a backing dish.
Put( in the hole of the removed stems) a little piece of butter (and optionally- a very little piece of cheese), add a pinch of salt, black pepper and your favorite mixed spices( and optionally seeds- sesame, poppy, etc).
Bake for 10 minutes.
Serve hot or cold.