Heat the oil in a large saucepan over medium heat. Add the leek, carrot and celery, then cook, stirring, for 3-4 minutes until softened. Add the tomato paste and cook for 1 minute. Add the lentils and stock and bring to the boil. Reduce heat to medium-low and simmer gently for 1 hour, skimming the surface occasionally, until the lentils are tender.
Add the tomato, cannellini beans, coriander, paprika and some salt and pepper to the pan, then cook, stirring occasionally, for a further 20 minutes or until soup is thick. Taste for spices and seasoning, then stir in half the parsley.
Divide soup among shallow bowls and top with remaining parsley, a drizzle of extra virgin olive oil and freshly ground pepper