Beyond perfectly cooked and expertly sliced roast beef, the “weck” aspect of Buffalo’s favorite sandwich is essential. From the German word Kummel, meaning caraway seed, a kummelweck looks vaguely like an ordinary hard roll spangled with caraway seeds and coarse salt. But it is not ordinary. A correct weck is delicate, its freshness evanescent. Lightness is crucial because the roll cushions, but must not compete with, the extreme gentle feel of the sliced beef. On the other hand, it cannot be too fragile, for the customary way of assembling the sandwich is to briefly immerse the top half in pan juice just long enough for it to start to soften before it is set atop the beef.