4 tablespoons unsalted butter
1 medium carrot, finely chopped
1 stalk celery, finely chopped
1/2 medium onion, finely chopped
2 cups cooked chestnuts
1 cup port wine
1 sprig thyme
2 cups chicken stock
1/2 cup heavy cream
Salt and pepper to taste
Melt butter in a medium saucepan. Add the carrot, celery and onion and cook until softened, about 10 minutes. Add the chestnuts and cook for 5 minutes. Add the wine and thyme and cook over medium-high heat until the wine is reduced by half, about 5 minutes. Add the chicken stock and bring to a boil.
Cover partially and simmer over low heat for 30 minutes. Discard the thyme sprig. Add the cream to the soup. Working in batches, purée the soup in a blender. Return soup to the saucepan and bring to a simmer. Season with salt and pepper and serve.