2 tablespoons fresh chives ( or scallions) for garnish
Cut leeks in half length wise. Rinse to remove any dirt. Slice leeks into ¼ inch half rounds. Heat oil in medium sized heavy bottom pot or dutch oven, over medium heat. Add leeks and sauté until tender, golden and fragrant, 8-10 minutes.
Add garlic and sauté for 3 more minutes.
Add potatoes, stock and fresh thyme. Bring to a boil, turn heat to low and simmer, covered, for 15-20 minutes, until potatoes are fork tender.
Blend in batches, until very smooth and silky —remember, you don’t want to fill up a blender with hot liquid, or you will have a soup explosion –so blend in small batches, less than half full, with the lid held down very tightly, holding lid down firmly covered with a kitchen towel. Or use an emersion blender.
Return the silky smooth soup to the pot, bring to a simmer over low heat, and stir in the sour cream. Taste and adjust salt and pepper.