Steak Pierre

With a mallet, pound a well trimmed steak very thin. Melt the butter in a chafing dish, then add the sherry, mustard, chives or green onions, capers, and mushrooms. Salt and pepper the steak and cook it in this mixture turning it once. Set the steak aside and keep it warm. Add lemon juice and parsley to the remaining liquid in the chafing dish. Simmer quickly, pour over steak and serve.