FRIDAY NIGHT DINNER--Sweet Potato and Leek Soup

                                 SWEET POTATO and LEEK SOUP
              adapted from an old issue of the Sunday New York Times Magazine

• 8 medium leeks, white parts only
• 12 strips double-smoked bacon
• 6 tablespoons unsalted butter
• 2 medium sweet potatoes, peeled and thinly sliced
• 6 cups chicken stock
• salt & freshly ground black pepper, to taste
• 3 tablespoons snipped fresh chives

1.  Thinly slice the leeks, place in colander and rinse under cold water.
2.  Finely chop the bacon and fry in a kettle over medium heat.  As it cooks, drain off and reserve the fat, and remove the bacon to a plate lined with paper toweling.  Set aside.
3.  Wipe the kettle clean and add 2 tablespoons of the reserved bacon drippings along with the butter.  Over low heat, sweat the leeks, stirring occasionally, until they are very soft, about 25 minutes.
4.  Add the sweet potatoes and stock, cover and bring to a boil.  Reduce the heat and simmer uncovered, until the potatoes are very soft, about 35 minutes.
5.  Transfer the soup in batches to a blender or food processor and purée until smooth.  Season with salt and pepper to taste.  Stir in half of the cooked bacon and the 3 tablespoons chives.
6.  To serve, ladle the soup into bowls and top with remaining bacon.