Gratin Dauphinois (Potato Gratin)

These potatoes are so good, such a superior partner to roast lamb or beef, that they may be the only vegetable gratin that has never gone out of fashion. Gratin dauphinois originated in the former province of the Dauphiné in southeastern France. I prefer using American light cream (20 percent fat) to heavy cream, which can be twice as fatty, and of cour…