Cut the meat into small pieces or slice thinly. Combine with the other ingredients in a glass bowl and refrigerate for at least 1 hour (or before you go to work in the morning).
Melt the butter in a medium saucepan and add marinated chicken and chopped onion.
Stir constantly until the chicken is sealed (white looking) and the onion is soft, add the dried spices and ginger, then stir in the tomatoes and chicken stock. When simmering, pour in the basmati rice, stir, and simmer for 10 minutes.
Mix together the tomato paste and flour and whisk, a little at a time, into the soup. Add the brown sugar and cream and season to taste.
Serve in soup bowls with a dollop of natural yoghurt, chopped fresh coriander and torn up naan bread for dunking.