1Heat the oil in a large frying pan. Saute onion and potato for 3 minutes or until the onion has turned translucent.
2Pour in the stock and bring to the boil. Once boiling, add celery and a bit of nutmeg. Bring back the boil and lower the heat.
3Add celery salt. Let simmer for 20 minutes.
4Puree the soup with a hand blender, liquidiser or food processor until smooth. Serve with wholewheat croutons.