Heat the oil in heavy bottomed pan or karahi.
Add the onion and gently fry for 5 minutes.
add the sultanas to the pan if using and continue to cook, stirring as needed until the onions start to go golden
Add the garlic and ginger and fry for 30 seconds more
Add the curry masala and cook gently, stirring for 40 seconds. If it's starting to stick add a splash of water.
Add the chicken to the pan and stir round to coat with the spices.
Add enough water to not quite cover the chicken and bring to a simmer.
Add the salt, tomato ketchup and Worcestershire sauce.
Cook for gently for 20 to 30 minutes or until the chicken is cooked.
If using add the coriander, stir through and serve with plain rice.