Heat oil on medium heat in medium saucepan. Add onion; cook and stir 5 minutes or until softened. Stir in garlic; cook 1 to 2 minutes or until fragrant. Add potatoes, milk, stock and Seasoning; cover. Bring to simmer. Cook 10 to 15 minutes or until potatoes are fork tender. Stir in crème fraiche.
With center part of cover removed to let steam escape, puree mixture in batches in blender on high speed until smooth. Return pureed mixture to saucepan. (Or puree mixture in saucepan with an immersion blender.) Garnish with chopped chives, additional crème fraiche and sprinkle with additional Seasoning, if desired.