In a one gallon soup pot heat oil or butter on a medium flame. Add the shallots, mushrooms and salt to the pot. Sweat for about 10 minutes or until the vegetables are tender.
Add sherry wine and continue to saute until the pot is almost dry. (Add in the flour and stir for another five minutes (optional)).
pour the vegetable stock into the pot while whisking the the vegetables and broth. Raise the heat to High until the soup begins to boil. Once boiling reduce the heat to low medium and let the soup simmer, with the lid ajar, for 30 minutes.
Puree soup in a blender until creamy. If you are using a vitamix ladle the soup into the blender only half way. Cover the lid with a dish towel and slowly turn the blender up to the highest setting. Repeat until all of the soup is blended. Return to the pot to reheat and add fresh pepper.