Put the tomatoes, tomato purée, garlic and ginger in a blender or food processor with the stock and whizz until smooth. Pour into a large pan and add the chipotle, ¾ of the coriander, green pepper, most of the chilli and seasoning. Bring to a simmer and cook on a medium heat for 10 minutes, then add the rice and cook for another 10-15 minutes or until the rice is tender. Add a little water or stock if the soup is too thick. Serve in bowls with a dollop of yogurt, the rest of the coriander and chilli, and a generous grinding of black pepper.