Wash a dozen good sized mushrooms, either Lactam or Agarici, also wash and remove the pores from half a dozen good sized "beefsteak" mushrooms, cutting them into slices. Put all these into a baking pan, sprinkle over a half teaspoonful of salt, add a tablespoon-ful of butter, and bake in a moderate oven three-quarters of an hour. Broil the steak until it is nearly done; then put it into the pan with the mushrooms, allowing some of the mushrooms to remain under the steak, and cover with the remaining portion; return it to the oven for ten minutes; dish and serve at once.