1. Cook the garlic, and white part of the leek in the olive oil till tender. 2. Add the stock and diced potatoes, green parts of the leek and simmer till the potatoes are tender. 3. Add the herbs and cook for 10 minutes. 4. Puree soup in a blender, food processor or with the hand immersion blender as I am doing now. I blend for a good long time until the soup is light and silky smooth. 5. Add the milk or cream, and season with salt and pepper. 6. Serve topped with some herbs and a dollop of sour cream.