Pike, Pike-Perch, or Salmon with Beurre Blanc

Beurre blanc, the famous Loire Valley sauce typically served with poached fish, especially brochet (pike), sandre (pike-perch), and salmon, is made all along the middle and lower part of the river. The sauce, which soon became widespread in home cooking, was invented in about 1890 by Clémence Lefeuvre at her then-modest restaurant outside the city of Na…