I think a lot of us are fixated on the idea that that gratins must always be insanely unhealthy — swimming in cream, broiled in cheese, topped with butter — and that ones made with anything less are simply inferior gratins. It’s a shame really, because I think it keeps us away from them on weekday nights, when they could be our best friends, as they can be made in advance, reheat like a dream and can be spooned off as needed. They can be side dishes to a roast, cutlet or fish or they can be the bed in which you nest a poached egg, tear off pieces of a baguette and call it a heavenly meal.