Bechamel

Béchamel sauce is one of the mother sauces of French cuisine, made from a white roux (butter and flour) and milk, seasoned with ground nutmeg. The first recipe of a sauce similar to béchamel is in the book Le cuisinier françois by François Pierre de La Varenne in 1651, made with a roux, as in modern recipes. The name of the sauce was given in honour of Louis de Béchameil, a financier who held the honorary post of chief steward to King Louis XIV of France in the 17th century. The first named béchamel sauce appears in The Modern Cook, written by Vincent La Chapelle and published in 1733, in which the following recipe for "Turbots (a la Bechameille)" appears:

Source: Wikipedia