Place the stainless steel inner pot inside the Instant Pot®. Add the potatoes and salt. Add enough water to cover the potatoes.
Close and lock the Instant Pot® lid. Make sure the steam release handle is turned to Sealing. Press Pressure Cook, pressure level High, and set time to 10 Minutes.
Once the time is up, press Cancel and turn the steam release handle to Venting. Once all steam has been released, open the lid and remove the potatoes.
Put the potatoes in a bowl and mash. Add the butter and the milk. Stir. Season with salt to taste and serve hot.