Heat a large pot on medium high heat. Pour in your oil, and then add in your sliced onions. Fry till they start to get some color on them.
Add in the ginger garlic pastes. Cook for a couple of minutes until the raw ginger smell is gone. Do not brown, add some water if needed.
Add in all your whole spices, fry in the oil for a minute. Then add in all your dry powdered spices, half your salt, and a splash of water. Fry in the oil for a few minutes, adding more water if the curry starts sticking to the bottom. Reduce the water while stirring, until all the oils come out, them add in water again and repeat. The more times you do this step the better your curry will taste. Cut some slits onto your chicken pieces, add them into the curry, and fry for a few minutes, adding in a bit of water if needed to keep the bottom from burning.
Turn down to a mid-low simmer and leave to cook for 15 minutes with the lid on. Stir midway through, adding a bit of water if it's sticking.
Once your chicken pieces stop bleeding and is pretty much cooked, add in a cup of water, the rest of your salt, and your halved potatoes.
Submerge the potatoes in the water by pushing the potatoes to the bottom, then simmer on mid-low with the lid on for about 10 minutes or until your potatoes are fork tender but not super soft.
Add in green chilis and a dash of cumin (optional), simmer for another couple of minutes, then garnish with cilantro and you're done! Serve hot with rice or rutis and enjoy!