Melt the butter in a large sauce pot, then add the shallots, leek, carrot and celery. Sauté the vegetables until slightly reduced, approx 5 minutes.
Add the potatoes, chestnuts, broth, bay leaves and the seasoning, and simmer for 20 minutes. Remove and discard the bay leaves. Then puree your soup, using an immersion blender. Add the tofu and puree once more, until smooth and creamy.
Serve garnished with chives and whole or chopped chestnut pieces, if desired.
You may use water or broth to sauté the vegetables if you're avoiding oil.If using a stand blender to puree your soup, use extreme caution and do so in batches to avoid burns.This soup can be fully made ahead and refrigerated one day in advance. Just reheat and serve. (In fact, this soup tastes better the next day when the flavours have had some time to absorb.)Leftovers keep refrigerated for up to 3 days, or freeze for up to 1 month.