In a medium saucepan, combine broth, celery, onion, and carrot. Bring to boiling; reduce heat. Cover and simmer about 20 minutes or until vegetables are very tender. Cool slightly.
Transfer half of the vegetable mixture to a blender or food processor. Cover and blend or process until smooth. Repeat with remaining cooked mixture. Return all vegetable mixture to saucepan. Stir in corn, whipping cream, thyme, black pepper, and hot pepper sauce. Heat just until simmering.
Stir in crabmeat and/or shrimp; heat through. If desired, garnish with croutons and fresh thyme. Makes 4 or 5 servings.