1. In a small bowl stir together sour cream and buttermilk. Set aside.
2. Place green onions and celery in the bowl with the ultrablade knife. Mix at speed 12 for 10 seconds and scrape down the sides and bottom of the bowl.
3. Add olive oil to bowl and launch the P1 simmer program.
4. Add sour cream mixture and all remaining ingredients, except chives, and launch the P1 soup program.
5. If a creamier soup is desired, mix at speed 10 for 1 minute. Garnish soup with chopped chives, sour cream mixture. Serve with crackers.