In a food processor or with a mortar and pestle, blend the spice paste ingredients together. Set aside
In a large wok, heat 1 tablespoon oil. Fry the onions until fragrant and add the spice paste. Fry until fragrant and the paste turns a few shades darker.
Add the curry leaves, cinammon stick, star anise and cloves and fry for a few minutes before adding the chicken. Coat the chicken pieces with the spice paste and cook until lightly browned to seal in the juices.
Add the water and potatoes and simmer until the chicken is cooked through and the potatoes are done.
Add soya sauce and tomatoes and cook for another 5 minutes. Serve hot with rice or French bread.