Set the IP to saute mode. Add 4 tbsp oil, green chillies, ginger slices and whole dried red chillies. Allow to saute for a minute or so till they get fragrant.
Add the marinated chicken along with all the marinade. Saute for 8-10 minutes, stirring often till the chicken is almost cooked through. Making sure to stir well so nothing is sticking to the bottom of the pan. (If you are using bone-in chicken see the recipe notes below). You will see the oil start to come to the surface of the curry when it is done.
Add the potatoes, stir well to coat the potatoes in the curry.
Gently pour the rice and water into the curry.
Add the raisins, if using, spreading them out in an even layer on top of the rice.
Cancel saute mode. Close the lid, set the vent to sealing, and cook on high pressure for 6 minutes. Quick release the pressure.
Once the pressure is released, open the IP lid and gently fluff the rice and chicken with a silicone spatula a few times to mix the chicken and rice a bit and break up the flat surface of the rice on top. Make sure to get down to the bottom of the pan to get the chicken. Be gentle so as not to break up the rice.
Pour the saffron water over the rice in a circular motion to coat as much rice as possible. Sprinkle the top of the rice with the reserved brown onions, black pepper and cumin seeds. Cover again and allow to steam for 10 minutes in the residual heat before serving. Enjoy!