Put the flour in a salad bowl or earthenware tureen, leaving a bare space in the centre of the basin. In this put the yolks of eggs mixed with melted butter. Work with a wooden spoon, gradually mixing in the flour with the eggs and butter till all the flour has been used. Finally add the whites of eggs, beaten to a stiff froth. The paste should be very firm, although light. Shape into small balls, either with the hands or with a soup spoon, and poach in boiling stock for 10 minutes. When the balls rise to the surface they are done.