Sauté onion and celery until soft and translucent; set aside
Add chopped potatoes to chicken broth in sauce pan, and boil until potatoes are fork tender, about 12 minutes
After cooling for a few minutes, spoon the potatoes into a blender, carefully pouring in some of the hot broth and adding the onion and celery.
When thoroughly blended, pour back into sauce pan. It should be fairly thick at this point. (If it seems a little too thin before adding milk, boil for a few minutes until thickened.) Then add milk or cream to desired consistency.
Add salt and pepper to taste
Blend in ¼ cup of sour cream
Garnish with the rest of sour cream, grated cheddar cheese and chopped chives