Sauce béchamel has long been a mainstay in both professional and home kitchens. In the 1970s and ’80s, however, the reaction against flour-thickened sauces became so vehement that this one-time cornerstone of classic French cooking was almost completely abandoned and replaced with sauces based on reduced cream. While these cream-based versions have their merits, the straightforward appearance and flavor of a béchamel-covered gratin will often satisfy a deeper need than a refined and intricate cream sauce.