Put the chicken stock and potato pieces in a large saucepan and bring to a boil. Put the lid on, reduce the heat and let the mixture simmer for 5 minutes.
Wash the spinach thoroughly and drain. Remove the stalks from the spinach with a sharp knife and discard. Roughly chop the leaves and place in the saucepan. Cover and simmer for 3 minutes. Add the sour cream and parmesan cheese and stir well. Take the pot off the stove.
Pour the mixture in portions into the food processor or blender and puree. Return the mixture to the saucepan and heat over a medium heat for 1 minute while stirring. Garnish the soup with chives flowers or other fresh herbs, if desired.