Heat the oil in a pan large enough to hold the chicken pieces without having them overlapping. Fry the sliced onions until transparent, then add the ground walnuts and continue cooking., stirring constantly for 3-4 minutes, or until onions mix with the walnuts to make a paste.Remove this mixture from the pan, squeezing out as much oil as possible.

Cook the chicken in the oil left in the pan until the pieces are well sealed on all sides. Return the paste to the pan, pour in the water, then add the salt and the cinnamon. Cook, covered for about 15 - 20 minutes, or until chicken is cooked. Pour in the tamarind extract, then toss in the curry leaves and sugar. Uncover the pan and continue to cook gently for a further 5 minutes. Re-cover the pan and leave over a low heat for 10 minutes before serving.