Melt butter in Dutch oven over medium heat. Cook onion in butter, stirring occasionally, until tender. Stir in broth, squash, 2 sliced pears, thyme, salt, white pepper and coriander. Heat to boiling; reduce heat. Cover and simmer 10 to 15 minutes or until squash is tender.
Pour about half of the soup into food processor or blender. Cover and process until smooth; pour into another container. Repeat with remaining soup. Return soup to Dutch oven.
Stir whipping cream into soup. Heat over medium heat, stirring frequently, until hot (do not boil). Garnish with sliced unpeeled pear and pecans.