1. Boil water. Add beans and boil 2 minutes.
2. Remove from heat. Cover and let stand 1 hour.
3. Saute celery and onion. Add to beans.
4. Strain soup and return liquid to the soup pot.
5. Puree vegetables and return to soup pot.
6. Add bouillon.
7. Put yogurt in a bowl. Remove 1 cup soup broth and add to yogurt. Mix well. Return to soup pot and stir until blended.
8. Cover and simmer.