Ivory, crunchy slices of Jerusalem artichoke are bathed in a mustard-spiked, creamy dressing and served with watercress for a salad that may become a regular in your home, as it has in mine.
Combine egg yolk, shallots, mustard, vinegar, cayenne, and salt in a small bowl; blend with a whisk. Gradually incorporate oil, whisking vigorously. Reserve.
Trim the chokes into fairly even-sized large pieces. Using slicing blade of a processor, a vegetable slicer, or a mandoline, cut chokes into very thin slices.