1 lb Japanese or Kirby cucumbers (about 5)
1/2 teaspoon wasabi powder
1/2 teaspoon water
2 tablespoons rice vinegar (not seasoned)
1 tablespoon sugar
1/4 teaspoon soy sauce
Equipment: an adjustable-blade slicer
Very thinly slice cucumbers crosswise with slicer; toss with 1 teaspoon salt and drain in a colander 15 minutes. Rinse cucumbers under cold water, then squeeze handfuls to remove excess water; pat dry.
Stir together wasabi powder and water in a bowl and let stand 5 minutes. Add vinegar, sugar, and soy sauce, whisking until sugar has dissolved. Add cucumbers and toss well.
Cooks’ note: Cucumbers can be made 1 day ahead and chilled, covered.