2 medium fennel bulbs (sometimes called anise; about 1 3/4 lb), stalks cut off and discarded
3 celery ribs, cut diagonally into 1/8-inch-thick slices
Special equipment: a Japanese Benriner* or other adjustable-blade slicer
Directions
Whisk together vinegar, mustard, salt, and pepper in a large bowl. Add oil in a slow stream, whisking, until combined.
Cut peel, including all white pith, from oranges and grapefruit with a paring knife. Working over a bowl, cut segments free from membranes. Squeeze juice from membranes into a small bowl, then whisk 3 tablespoons juice into vinaigrette. Drain citrus segments, then add to vinaigrette.
Quarter fennel bulbs lengthwise, then cut lengthwise into paper-thin slices (about 1/16 inch thick) with slicer. Add to fruit along with celery and toss gently to combine.
Available at Asian markets, many cookware shops, and Uwajimaya (800-889-1928).
