In the Instant Pot, put on sauteé mode and add the butter, onions, and garlic. Sauteé it for a couple of minutes to strengthen the flavor.
After a couple of minutes, add the rest of the ingredients into the Instant Pot. Mix well.
Turn on Instant Pot and and manual high pressure for 20 minutes.
When it's finished, vent the IP and take the chicken out.
Turn the Instant Pot back on sauteé mode and reduce the broth/milk down until it's thick. To help this process, you can add a tapioca flour slurry a couple of times until it's thick to your preference. (To make a slurry, add 1 tbsp tapioca flour with a small amount of water and mix into the liquid you are trying to thicken.)
After the sauce has thickened, add the chicken back in. Serve over rice and veggies!