Combine water, bouillon cubes, carrots, celery, potato, onion, parsley, salt, and pepper in a medium Dutch oven; place over medium heat, and bring to a boil. Reduce heat; cover and simmer 40 minutes or until vegetables are tender.
Transfer vegetables and cooking liquid to container of an electric blender; process until smooth. Add butter, cornstarch, basil, marjoram, thyme, and Angostura bitters; process until well blended. Return mixture to Dutch oven.
Stir in milk; cook over low heat, stirring constantly, 5 minutes or until mixture thickens. Add 1 cup sour cream; mix well.
Ladle soup into individual serving bowls. Garnish with remaining sour cream and chopped chives. Serve warm.