Sometimes simply called white sauce, bechamel is essentially milk thickened with a roux made by cooking together flour and butter. Older recipes were somewhat more elaborate and contained mirepoix—diced celery, carrots, and onions— cooked in butter before the flour was added and sometimes a bit of unsmoked bacon or air-cured ham. A bouquet garni, rarely called for in modern recipes, was also included. Depending on how you are using the sauce, these are still worthwhile additions. But if you