In a 2 quart saucepan, combine potatoes, leek, stock and water. Bring to boil; cover and cook until potatoes are tender, about 10 minutes.
Transfer to an electric blender or food processor and blend until almost smooth.
Return soup to saucepan. Stir in the buttermilk. Bring to a simmer. Gradually add the cheese, stirring constantly until the cheese melts. Season with pepper and salt.
Garnish each serving with green onions or parsley.
Note: If you don’t have a blender or food processor, use a potato masher with a little of the stock.
Recipe by Living Full on Life at https://www.livingfullonlife.com/?p=1819