Put your Instant pot on sautee mode and let it heat up.
Add butter, garlic, white onion, and ginger. Sautee until golden brown
Add salt, pepper, chili pepper, garam masala, cumin into pot and stir to combine.
Add chicken
Add tomato sauce and milk and stir
Set your Instant Pot to MANUAL mode, HIGH for 3 minutes. When it is done cooking, manually release the pressure.
Set your Instant Pot back to sautee mode
Mix water and cornstarch together in a little bowl and add to butter chicken mixture, stir and let thicken. These last 2 steps are not necessary if you are using cream.
Serve with rice, naan, wedge of lime and some cilantro on top