Place some butter in a frying-pan and let it cook just to the point of darkening, but be very careful not to burn it. Throw in some small sprigs of parsley and let them fry. Then pour it over the fish. At once place a little vinegar in the frying-pan, and as soon as it is hot pour it also over the fish and serve at once.
Put into a frying pan the necessary amount of butter, and cook it until it has a brown color and begins to smoke. At this moment add a large pinch of concassed parsley leaves and spread it immediately over the object to be treated.