Wash the mushrooms under running water, peel the caps and trim the ragged ends of the stalks. Put into a baking-dish, gills of the mushrooms uppermost, sprinkle with salt and pepper and a very little mace and put a tiny piece of butter on each. Cover and cook 25–30 min. in a fairly hot oven (375° F-, Gas 5).
If possible, cook in a fireproof glass dish with a lid and serve in the same dish, thus retaining all the flavour of the mushrooms.