CHILLED CELERY SOUP

Steps:

• 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.