- Roughly chop the onion, crush the garlic and add to a large saucepan with the olive oil.
- Saute for 5 minutes.
- Add the celery and stock, stir to mix and then add the sweet potatoes.
- Cover and cook for 15 minutes.
- Transfer to a blender and add the watercress.
- Return to the pan and stir in the miso.
- Serve garnished with a sprig or two of watercress.