Melt the butter (if using) in a large soup pot over medium-high heat. Add the chopped shallot, leek, carrot, and celery. Sauté until slightly reduced, approx 5 minutes.
Add the potatoes, chestnuts, broth, bay leaves, and seasoning. Bring to a boil, then lower the heat and simmer for 20 minutes, and stir occasionally. Turn off the heat and remove/discard the bay leaves. Then use an immersion blender to puree the soup. Add the tofu and puree again until smooth. Taste the soup and add salt and pepper if needed.
Serve garnished with chives, cashew cream, chopped chestnut pieces, and/or vegan bacon bits if desired.
Video
Notes
For oil-free, use 3-4 tablespoons of water or broth to sauté the veggies and skip the vegan butter.If you don't have an immersion blender, you may transfer the soup in batches to a stand blender. Use caution when pureeing hot liquids, and do not overfill the blender.Make the soup in advance if time allows, as the flavours get even better the next day.Leftovers keep refrigerated for up to 3-4 days or freeze airtight for up to 3 months.