Select the Sauté - More setting on the Instant Pot. Once hot, add the oil, ghee, and onion, and sauté until the onion turns golden, about 10-12 minutes.
Add the garlic and ginger and continue to sauté until the raw smell disappears, about 15-20 seconds.
Add beef (along with bones) and sauté for about 4-5 minutes or until it begins to brown.
Press the Cancel button to turn off the Instant Pot. Add the whole spices, powdered spices, and salt and sauté for about 20 seconds. Pour in the water and stir to deglaze any browned bits from the bottom.
Secure the lid and set the Pressure Release to Sealing. Select the Meat/Stew setting and turn the Pressure Level to High. If using Beef Stew meat, pressure cook for the default 45 minutes. If using Beef Shank meat, increase time to 50 minutes.
Let naturally release for 5 minutes, then move the Pressure Release to Venting to release the remaining pressure. Remove the whole spices, if desired.
Take out a cup of the liquid of the Nihari into a bowl. Let it cool a little by adding an ice cube to it. Place the atta or roasted brown rice flour* in another bowl. Bit by bit, whisk in the Nihari liquid to the atta to form a smooth slurry (small clumps are okay). Slowly stir this slurry back into the Instant Pot to prevent clumps. Taste and adjust salt & seasoning as desired.
Secure the lid again and set the Pressure Release to Sealing. Select the Pressure Cook setting and set the cooking time for 10 minutes at low pressure. Let naturally release for 5 min. If needed, select Saute - High to reduce down and thicken the nihari to desired consistency.
Sprinkle with cilantro and serve alongside the garnishing with naan.
*Traditionally, atta flour is used to thicken the curry. For a gluten-free option, dry roast the brown rice flour in a non-stick pan over low-medium heat for 4-5 minutes. Stir constantly to ensure even roasting.*If you do not use the pre-made store-bought Nihari Masala, increase the rest of the spices per taste. You can also try adding ginger powder, onion powder, and garam masala to boost flavor.