In a large saucepan, bring first five ingredients to a boil. Reduce heat; cover and simmer for 15-20 minutes or until vegetables are tender. Cool.
Puree mixture in a food processor or blender; set aside. In the same saucepan, saute fresh tomatoes in butter for 5 minutes. Stir in flour to make a smooth paste. Gradually add cream and stir over low heat until thickened. Stir in pureed mixture and sherry if desired.