Add the tomato sauce, minced garlic, minced ginger, mild curry powder, Garam Masala, paprika, salt, and onion powder (if using) and mix together.
Add in the diced chicken thighs and butter.
Cover your Instant Pot and set the valve to the sealing position.
Select Pressure Cooker / Manual Setting, and set to high pressure for 6 minutes.
When cook time is done, let the pressure release naturally for 5 minutes before performing a quick pressure release.
Remove the chicken pieces from the Instant Pot, turn the Instant Pot back on to the Sauté mode add in the coconut milk, stir to combine, and let simmer for a few minutes for the butter sauce to thicken.
When done, switch off the heat, add the chicken pieces back in, adjust any seasonings, and then serve.