Put the cashew nut into a bowl and pour hot water onto them, enough to cover the cashews completely. Cover and leave until needed.
To make the spice mix: Remove the green and black cardamom seeds from the pods. Discard the cover and add the seeds into a mortar and pestle (or a grinder), along with black peppercorns and mace.Grind until a homogenous (coarse) powder is formed. Rub the nutmeg onto a fine grater to add about a pinch of it into the spice mix (or add nutmeg powder, if using).
Put a pot on medium heat and add the ghee. Once the ghee has melted, add the onion and fry, stirring frequently until it is golden brown.
Once the onion is golden brown, turn off heat and immediately take the fried onion out from the pot, skimming the fat (leave the remaining ghee into the pot). Set the fried onion aside until needed.
Put the pot back on medium heat with the remaining ghee. Once hot, add the chicken and spread it all over the pan. Let it brown for a minute, then flip and saute from the other sides as well.
Once the chicken has changed color on all sides, add the ginger-garlic paste and mix. Saute for a minute.
Turn heat on low. Add the cinnamon stick, along with coriander powder, Kashmiri red chili powder, turmeric powder and salt. Mix thoroughly and let cook for 10 minutes, stirring occasionally. Add small splashes of water to prevent the spices from burning.
In the meantime, let's prepare a paste. Add the fried onion, the soaked cashews (along with the water) and yogurt to a blender. Blend until smooth. You can add some more water if it is too thick to be blended.
Back to the chicken: Add the prepared paste, spice mix and 150 ml water to the pot and mix to combine. Cover and let cook on low heat for 30 minutes (or until the chicken is completely cooked through).
Turn off heat and add kewra water. Mix to combine. Transfer to a serving bowl and serve with fresh, homemade naans.
