2 medium leeks (about 1 1/2 lbs.)
4 Tbs. unsalted butter
1 clove garlic, finely chopped
4 cups homemade, or canned, low-sodium chicken stock, or golden vegetable stock
About 1 tps salt, less if using canned stock
1 medium head romaine lettuce, with the outer, deep green leaves
1/4 cup fresh French tarragon leaves
Freshly ground black pepper
Optional garnish: creme fraiche or sour cream, and heavy cream
1-Cut off and discard tops of leeks at point where they turn from light to dark green. Split rest lengthwise in half, keeping roots attached so the layers won’t fall apart. Wash thoroughly. Thinly slice into half circles and discard roots. Melt butter in a large (4 quart) saucepan over medium heat. Add leeks, and garlic, and cook, stirring often, until softened and just beginning to turn golden, about 10 minutes. Add stock and salt (omit if using canned stock) and simmer. Turn heat to low and cover, and cook at a bubbling simmer for 15 minutes to further soften leeks. (The soup may be made up to this point up to two days ahead and stored covered in refrigerator.)
2–Slice whole head of romaine lettuce crosswise into one-inch thick strips (you don’t need to separate the leaves first) and discard the base. Wash and drain the lettuce. Stir the lettuce into the soup, increase the heat to medium, and cook uncovered until the lettuce is wilted and softened, about 5 minutes.
3–Stir in the tarragon leaves. Put half of the soup in an electric blender (you can use a food processor but the soup won’t be as smooth). Holding down the lid, turn blender on to low, then gradually increase to high until soup is very smooth. Pour the pureed soup into a second saucepan and repeat with the remaining soup. Gently reheat all the soup, tasting and seasoning if needed with salt and pepper. Serve in warmed bowls.
4–If you wish to garnish with cream, vigerously stir the creme fraiche with a teaspoon and thin it with cream until it falls off the spoon in a thick stream. Hold a spoonful of the cream about 6 inches above the bowl and let it fall in a circular or zigzag pattern onto the soup.
(Herb substitutions–Use 1 cup chervil, gently packed, or two Tbs. lovage leaves in place of the tarragon.)