In a large pan, sauté the onions, celery and carrots in butter until soft and the onions are beginning to turn translucent.
Add the chopped mushrooms, stir and then place the lid on the pan and let them sweat down for 10 minutes.
Add the stock and then the chestnut puree, let it simmer for 25 minutes before blitzing with a hand blender.
Serve in a small coffee cup with a swirl of single cream.
Feeds 8, served in small cups.