Boil softly in half a pint of well-flavoured pale veal gravy a few very thin strips of fresh lemon-rind, for just sufficient time to give their flavour to it; stir in a thickening of arrow-root, or of flour and butter, add salt if needed, and mix with the gravy a quarter of a pint of boiling cream. For the best kind of white sauce, see béchamel.