Creamy Chestnut Soup

Name: Creamy Chestnut Soup
Ingredients: 1 tablespoon unsalted butter; 12 ounces leeks , white and light green parts only, halved lengthwise, sliced thin, and washed thoroughly; 1 ripe Bartlett or Bosc pear , peeled, halved, cored, and chopped; 1 celery rib , chopped; 1 teaspoon minced fresh thyme; 1 bay leaf; Salt and pepper; 4 cups chicken broth; 3 cups (14 ounces) peeled cooked chestnuts , chopped; 3/4 cup half-and-half; 2 tablespoons brandy or cognac; 1/2 teaspoon sherry vinegar; Pinch ground nutmeg; 1/4 cup minced fresh chives