Special Equipment: An immersion blender, blender or food processor to puree the soup
Make The Soup: Slice the leeks in half lengthwise. Then slice two or three of the leeks crosswise into thin slivers until you’ve got 4 cups of thinly sliced leeks. Wash them well by swishing them in a bowl of water and then draining them in a mesh strainer, to be sure all the sand and grit is washed away. (save the remaining leeks for making frizzled leeks)
Place cubed potatoes, sliced leeks, 6 cups water and 1 teaspoon of salt in a large heavy soup pot or Dutch oven. Bring to a boil. Lower to a simmer. Cook, partially covered (to avoid splattering) for 20 minutes or until potatoes and leeks are nice and tender. Puree with an immersion blender or in your food processor. (Don’t over process). Season with salt and pepper to taste.
Make the Frizzled Leeks: Line a plate with paper towel. Cut the remaining leeks into 2 or 3-inch pieces. Then cut each piece lengthwise into thin slivers (see instructional photo in post). Wash and drain the leeks. Heat oil over medium heat until hot enough to sizzle a sliver of leek. Add leeks and cook for 8-10 minutes, stirring from time to time, until they’re light golden brown. Be very careful to monitor the heat so they don’t burn. Transfer the leeks to prepared plate to cool. Sprinkle with a pinch or two of salt. You can make them up to a day ahead and keep them at room temp in a tightly sealed container.
To Serve: Serve the soup hot. Ladle it into bowls. Add a dollop of sour cream, some frizzled leeks and some fresh cracked pepper to each bowl, just before serving.