Peel the kohlrabi and potatoes and cut into small pieces. Cut the tender leaves of the kohlrabi into very fine strips. Sauté the onions in the butter until translucent, add the kohlrabi and potatoes and sauté. Add leaves and sauté. Pour in the vegetable stock and cook over a moderate heat for about 8-12 minutes.
Remove some kohlrabi and potato pieces with a ladle and set aside. Add the milk and cream cheese to the saucepan, season and bring to the boil briefly. Then puree everything. Add the kohlrabi and potato pieces that were set aside and garnish with the parsley.