3 lg. potatoes, peeled and quartered
2 leeks, trimmed well, drained, and cut into julienne slices
3/4 c. creme fraiche or heavy cream (optional)
salt
freshly ground black pepper
3 tbsp. chopped tarragon or chervil for garnish

Combine potatoes and leeks in 1 quart of water in a large saucepan. Bring to a boil over high heat. Season with salt and pepper. Reduce heat and simmer gently until vegetables are soft, 35-40 minutes. Puree the soup in a food processor or blender. Return to saucepan. (Creme fraiche can be added now and cooked over low heat until heated through.) Heat over low heat. Adjust seasoning and serve garnished with the fresh herbs.