Place peeled potatoes in inner liner of Instant Pot. Add water.
Close the instant pot lid and turn pressure valve to seal. Cook on manual high pressure for 10 minutes.
When the cook time is complete press "Cancel" and move the valve to "venting" for a quick release of the pressure.
After the pressure has fully released, carefully remove the lid. Add the remaining ingredients and use a masher to mash the potatoes and combine the ingredients.