Cut the chicken into 5cm chunks and put them in a mixing bowl with salt and vinegar.
Mix well and set aside for 30 minutes
Preheat a small heavy-based pan over a medium heat and dry-roast the coriander seeds, cumin seeds, cinnamon, cloves, cardamom, fenugreek, chillies and curry leaves until they are dark, but not black.
Remove and cool then grind in a coffee grinder until finely ground. Set aside
Heat the oil in a medium saucepan and cook onion over a medium heat for 5 minutes, until translucent.
Add the ginger and garlic purees and continue to cook for 2 minutes.
Add the turmeric, chilli powder, chicken and spice mix.
Stir and mix well.
Add the lemon grass, tomatoes and warm water.
Bring to the boil then reduce the heat to low, cover the pan and cook for 25 minutes.
Add the coconut and stir until it has dissolved.
Cook for 7-8 minutes.
Remove from heat and searve with rice.