Remove the lid from an Instant Pot 3-quart mini machine, and press 'SAUTE.'

Add the butter to the pot, and let it melt.

Next, add the diced onion and bell pepper, and stir to coat.

Using a microplane, grate the garlic and ginger into the pan, and stir again.

Add all of the spices (garam masala, turmeric, paprika, cumin, and salt) and stir. Add a dash of cayenne pepper if you want it spicy.

Stir everything in the pot together very well, and then turn OFF the Instant Pot.

Add the tomato sauce and chopped chicken thighs to the pot. Stir to coat everything.

Next, press 'PRESSURE COOK' on the Instant Pot, and toggle to 'HIGH.' Place the lid on the Instant Pot, turn the dial to 'Sealing,' and set the timer for 10 minutes.

Once the pot comes to pressure, the 10-minute countdown will begin. Consult your Instant Pot manual for any troubleshooting.

When the 10 minutes is up, do a 'forced pressure release' by covering your hand with a thick kitchen towel, and turning the sealing valve to 'venting.' Be careful--lots of steam will pour out of the valve.

When the pressure is done releasing, the float valve will drop, and it's safe to open the lid.

Meanwhile, whisk together the heavy cream and cornstarch very well. Remove the lid from the Instant Pot, and stir in the heavy cream and cornstarch mixture.

Let the mixture thicken a bit with the residual heat, and then serve over white rice and with chopped cilantro on top.