1.Saute celery and onions in oil until softened.
2.Add vegetable broth and let simmer for about 25 minutes.
3.Place cooked ingredients, buttermilk, potatoes, garlic, salt, and pepper into the Vitamix container in the order listed and secure lid.
4.Select Variable 1.
5.Turn machine on and slowly increase speed to Variable 10, then to High.
6.Blend for 2 minutes.