Though various sources say it was first known as `` sauce Isigny '' ( a town in Normandy said to have been renowned for the quality of its butter ) . , Mrs. Isabella Beeton 's Household Management had recipes in the first edition ( 1861 ) for `` Dutch sauce , for fish '' ( p. 405 ) and its variant on the following page , `` Green sauce , or Hollandaise verte '' . Though various sources say it was first known as `` sauce Isigny '' ( a town in Normandy said to have been renowned for the quality of its butter ) , Mrs. Isabella Beeton 's Household Management had recipes in the first edition ( 1861 ) for `` Dutch sauce , for fish '' ( p. 405 ) and its variant on the following page , `` Green sauce , or Hollandaise verte '' .