Having cooked your steak, take it out of the frying-pan and keep it hot. Throw away the fat without washing the pan.
Put the anchovies and the butter in the same pan and let them melt, crushing them with a fork. Keep the pan over the heat and stir in the lemon juice, parsley and a turn of the peppermill. Add the juices from the steaks.
Arrange the steaks on hot plates and cover them with the sauce.