Beat the butter until soft and creamy. Add some pepper and then add the Marne French Mustard and sherry, stirring constantly. Form the butter into rolls with a diameter of about 4 centimeters and wrap the butter in foil. Roll the butter in the foil again. Place the butter in the refrigerator so that the butter can harden. Just before serving, cut the still cold butter into slices of about 1½ centimeters and place them on a platter. Vary with the mustard. Also try this recipe with Marne Grove Mustard or Marne Groninger Mustard.