Place the rinsed and scrubbed potatoes in the Instant Pot. Add 2 cups of water and 1 teaspoon of salt.
Cover and seal the Instant Pot. Set it to "manual" or "pressure cook" and adjust the timer to 20 minutes.
Once the time is up, use the quick release method to stop the cooking (refer to manual if needed).
Once the pressure is released, carefully take the cover off. Remove the potatoes with a slotted spoon and transfer to a plate.
Reserve about 1/2 cup of the cooking liquid in measuring cup and then discard the rest. Add the butter to the hot Instant Pot. Once the butter is all or mostly melted, add the milk, 1/2 teaspoon salt, and pepper. Whisk to combine.
If you are using a potato ricer, put the potatoes through that now as you add the riced mixture to the pot. (You can leave the skin on, though you will have to remove some of it from the ricer now and then if it starts to cover all the holes.) If you are using a handheld mixer or potato masher, leave the skin on and add those to the pot and then mash.
Once you get your desired consistency taste test and add the saved cooking liquid and more butter and salt as needed. Stir in the parsley or chives and enjoy immediately or keep warm in the Instant Pot for up to an hour or so.