If you can get your hands on fresh sorrel this is a nice flashy variation. Sweat some sorrel in butter. Follow the recipe above but omit the truffle salt. Puree the wilted sorrel in a bit of soup to make a sorrel puree. Ladle the soup into the bowl and then spoon some of the sorrel puree into the middle of the soup. Cut through the circle with a knife to drag the green sorrel puree through the white leek and potato soup. Prepare for adulation from your dinner guests and serve.