In a medium saucepan cook carrots in water for 15 to 20 minutes or until very tender. Drain in a colander. Add half of the carrots and half of the chicken broth to a blender container or food processor bowl. Cover and blend or process until carrots are smooth; transfer mixture to a large mixing bowl. Repeat with remaining carrots and chicken broth. Stir in white pepper and ground ginger. Cover and chill for 2 to 24 hours.
Before serving, stir in sour cream. Top each serving with celery leaves, if desired. Makes 4 to 6 servings.