- In a large saucepan, heat the olive oil over medium heat. Add the leek and celery, and stir to coat in the oil. Cover, reduce heat to low and cook for 5 minutes, or until the leek and celery have softened. Do not brown.
- Add the parsnips and cover with the stock. Turn heat to high and bring to the boil. Reduce heat, cover and simmer for 15 to 20 minutes, or until parsnips are soft. Add the parsley and cook a further 3 minutes.
- Puree the soup in batches in a blender or food processor. Add the yoghurt to one of the batches and blend till incorporated. (Alternatively, use an immersion blender right in the pan.)
- Transfer the pureed soup back to the pan and reheat over medium heat. Slowly add the milk whilst stirring, using only as much as you need to achieve your desired consistency. Add salt and pepper to taste.
- Serve topped with additional chopped parsley and grated Parmesan cheese, if desired. Enjoy!
Time saving tip
Since you are pureeing the soup, you can roughly chop the veg, and you needn't bother chopping the parsley at all. You can use the stems of the parsley, too!
Parmesan cheese is not truly vegetarian, as it contains animal rennet. To make this dish 100% vegetarian, omit the cheese or find a suitable vegetarian substitute made without animal rennet. In supermarkets look for the 'parmesan style hard cheeses' which are suitable for vegetarians.