Heat butter in a medium saucepan. Add the onion, celery and carrot and saute a few minutes to begin the cooking process. Sprinkle on the flour and cook a minute or until slightly browned. Add the broth, cover and simmer 15 minutes or until tender. Add chestnuts or puree and simmer for 5 to 10 minutes longer.
Puree in a blender or food processor and return to a saucepan to reheat. If too thin, simmer over low heat, stirring continuously until thickened or if too thick, add more liquid. Season to taste with salt and pepper, add a dash of Madeira and ladle out. Garnish with sour cream and chives if you wish.