Foie gras, the fattened liver of specially raised ducks or geese, is always expensive and never served without a little fanfare. It’s truly a special-occasion ingredient, one usually reserved for birthdays, anniversaries, Christmas, or New Year’s Eve. Foie gras is available everywhere in France but only at a limited number of specialty markets in America. However, the same high-quality foie gras used by chefs is available to us online (see Sources, page 514). Always buy your foie gras from a reliable merchant who does a lively business in it or who has special-ordered it for you, and when you get it, use it — it’s not an ingredient that keeps well.