Turn the Instant Pot to Sauté mode and heat the oil. Add the sliced onions and cook until soft and translucent.
Add the ginger-garlic paste and sauté for about a minute until fragrant. Add the chicken pieces and stir until they lose their pink color.
Sprinkle in all the spice powders and salt. Add the sliced tomatoes and cubed potatoes to it. Give it a good mix. Press Cancel in the Instapot.
Pour in the coconut milk and add a little water if you prefer a thinner curry. (Keep in mind that the chicken will release its own juices while cooking.) Throw in the green chilies, close the lid, set the valve to Sealing, and pressure cook on High for 10 minutes.
Release the pressure: Once the cooking time is complete, carefully perform a slow manual pressure release by turning the pressure valve to Venting.
Open the lid and give the curry a gentle stir. Lightly mash the cooked potatoes with a fork so they blend into the gravy, creating a rich and creamy texture.
Final touch: Crush the kasuri methi between your palms and stir it into the curry. Garnish generously with freshly chopped coriander.
Serve this creamy chicken curry hot with flaky parathas, soft rotis, or steamed basmati rice.