Which sauce is traditionally made from flour and milk?
Béchamel sauce is a sauce traditionally made from a white roux (butter and flour in a 1:1 mixture) and milk. Béchamel sauce is one of the "mother sauces" of French cuisine.
Some legends attribute the invention of béchamel to Louis de Béchameil, a financier who held the honorary post of chief steward to King Louis XIV of France in the 17th century. Others assert that it was brought to France from Italy in 1533 and named for the flour and water beautifying masks, 'balsamo,' used by women in Florence. The first named béchamel sauce appears in "The Modern Cook", written by Vincent La Chapelle and published in 1733.
Béchamel can be used as is in dishes such as Lasagne al Forno (Italian) or Moussaka (Greek), or as the base for other sauces such as Mornay sauce, which is béchamel with cheese.