- 1 medium leek (white and pale green parts only), chopped (1/2 cup)
- 6 cups chopped celery (about 12 ribs)
- 1 medium onion, chopped (1 cup)
- 1 tablespoon olive oil
- 1 small boiling potato, peeled and chopped (1/2 cup)
- 2 cups water
- 1 3/4 teaspoons salt
- Pinch of cayenne
- Wash leek well in a bowl of cold water, then lift out and drain.
- Cook celery, onion, and leek in oil in a 6-quart heavy pot over moderate heat, stirring occasionally, until softened, about 10 minutes.
- Add remaining ingredients (vegetables may not be fully submerged) and simmer, covered, until celery and potatoes are tender, about 10 minutes.
- Purée in batches in a blender until smooth (use caution when blending hot liquids), then force through a fine-mesh sieve into a bowl, pressing hard on solids, then discarding them. Set bowl in a larger bowl of ice and cold water. Let stand, stirring occasionally, until cold. Season with salt. Serve chilled or at room temperature.