I first enjoyed this soup in France, where the matriarch of the family with which I lived prepared it with fresh-roasted chestnuts from a street vendor. Upon arrival home in the United States, I had difficulty finding fresh chestnuts but discovered that unsweetened canned chestnut puree is a fantastic substitute (and a lot less labor-intensive). Prep: 15 minutes; Cook: 30 minutes; Cool: 15 minutes.
Melt butter in a large saucepan; add onion and celery, and sauté 4 to 6 minutes or until tender. Add chestnuts, and sauté another 2 minutes. Add Marsala, and scrape pan to deglaze. Add chicken broth and next 3 ingredients. Bring to a boil, reduce to a simmer over medium-low heat, and cook, uncovered, 20 minutes. Let cool 15 minutes.
Process soup in a blender, in batches, until smooth. Return to saucepan, stir in nutmeg, and bring to a simmer. While soup reheats, fill a soup tureen with boiling water, and let warm for several minutes; drain tureen. Transfer hot soup to warmed tureen, and serve.
*For testing purposes, we used Minerve brand whole roasted chestnuts.