Fill Instant Pot pot with 1 inch of water in the bottom, maximum 1 1/2 cups water.
Peel and chop the russet potatoes.
Place potatoes in an Instant Pot.
Add the teaspoon of salt.
Put the lid on top of the Instant Pot, and turn to close the lid.
Set the valve to “sealing”.
Press the MANUAL button. Press the +/- button to set to 12 minutes.
Let the IP do it’s job. It will take a little while for the Instant Pot to come to pressure. At which time it will start counting down.
When it counts to zero, it should beep. At this time, turn the valve/ vent to Venting. Immediately turn the steam release handle back to the Sealing position at the first sign of spattering. Quick Release should ALWAYS be closely attended.
Once the pressure cooker has vented, open it, and add the milk and butter, as well as salt and pepper to taste.
Use a potato masher to mash the potatoes right in the pot.