1 navel orange
1 1/2 tablespoons white-wine vinegar
1/4 teaspoon salt, or to taste
1/4 teaspoon black pepper
3 tablespoons olive oil
2 medium fennel bulbs (sometimes called anise; 2 lb total), stalks discarded
2 Belgian endives, trimmed

Special equipment: a Japanese Benriner* or other adjustable-blade slicer

Finely grate enough zest from orange to measure 2 teaspoons, then squeeze 1 tablespoon juice into a large bowl. Whisk in zest, vinegar, salt, pepper, and oil until combined well.

Cut fennel bulbs lengthwise into very thin slices with slicer. Halve endives lengthwise, then halve crosswise and cut lengthwise into 1/4-inch-wide strips. Add endive and fennel to vinaigrette and toss to combine. Chill, covered, 15 minutes to allow flavors to develop.