Watercress vichyssoise

1 boiling potato, peeled and cut into small pieces
1 small onion, finely chopped
2 cups vegetale or chicken broth
1 cup heavy cream
4 cups chopped watercress

Simmer potato, onion, broth, and cream, uncovered, until vegetables are soft, about 10 minutes. Stir in watercress and cook mixture, uncovered, over moderately low heat 3 minutes more. Purée soup in 2 batches in a blender until very smooth. Season with salt and pepper and let soup stand, uncovered, until cool, 45 minutes, then chill, covered, 1 1/2 hours.

Served with dark bread, sharp cheddar and fresh strawberries.