Make up 2 cups of vegetable broth and set aside.
Chop tomatoes, onion, celery, garlic and sweet potato (I like to leave the skin on my vegetables wherever possible but feel free to peel the sweet potato first).
In a large pot, heat the oil and fry off the onion, garlic, chilli and celery until they soften. If you prefer not to use oil, you can heat a shallow layer of the stock to do this.
Next add the tomatoes, sweet potato, salt pepper and basil. Give it a good stir and allow it to simmer for about five minutes.
Add the stock, cover and bring to the boil. Then simmer gently for about twenty minutes, stirring occasionally.
Now Is the part where I always make a mess. I allow it to cool slightly then pour it into a food processor and really give it a good blast. Blending it until it's smooth. Of course you can use a blender or stick blender to do this. Then back in the pot to be warmed up stirring through the plant milk.
Served with a nice crusty sourdough baguette.