Add the peppers, tomato, onion and stock to a saucepan and simmer on a low temperature for up to 20 minutes.

Once soft, add the saucepan contents into a blender until smooth.

Pour the contents from the blender through a sieve and press it through with a spoon, to get as much liquid soup as possible. This should leave the tough skins and some of the seeds behind (you can use the leftovers to make a tomato salsa).

Reheat the soup, as required. Add two tablespoons of yogurt and stir. Serve with a sprig of fresh basil on top.