Coat the chicken thighs with the Raj Curry Masala. Put to one side while you prepare the other ingredients
place the tamarind in small bowl and add just enough water to cover. Leave to soften, stirring and breaking it up occasionally.
Heat the oil in a large, heavy bottomed pan or kadai.
Add the onion to the pan and cook on a moderate heat until starting to brown, stir a needed.
Add the garlic and ginger to the pan and cook for 40 seconds.
Add the spice coated chicken to the pan and stir to seal the chicken all over. If the spices are sticking or burning add a splash of water.
Add water to the pan, just enough to come halfway up the chicken.
Strain the tamarind water through a sieve into the pan, using the back of a spoon to squash as much liquid through as possible.
Put a lid on the pan and continue to cook on a gentle heat for about 20 minutes.
After 20 minutes take the lid off, add the salt. Continue to cook for a further 10 minutes with the lid off. If it's too dry add a little water. If you want a thicker sauce, turn the heat up to reduce it a little.
Check that the chicken is cooked. Adjust the seasoning and add the fresh coriander if using.
Serve with some plain Basmati rice