Step 1

Set a wire rack in a 6-quart or larger Instant Pot or electric pressure cooker. Add the water. Place the potatoes on the rack. Lock the lid on and make sure the valve is set to seal. Set to cook for 20 minutes under HIGH pressure.

Step 2

When the cook time is up, let the pressure naturally release. Open the lid and transfer the potatoes to a large bowl.

Step 3

Add the half-and-half or milk and butter. Mash with a potato masher, food mill, or ricer. (Or whip the potatoes with a stand or handheld mixer on low speed with the paddle attachment. Do not use an immersion blender or food processor.) Add the salt, season with pepper if desired, and stir to combine. Taste and add more salt and pepper as needed.

Step 4

To keep the mashed potatoes warm, wash the insert of the pressure cooker to remove any cooking starch. Return the insert to the pressure cooker and coat the bottom and sides of the insert with the butter. Add the half-and-half or milk. Spoon in the warm mashed potatoes but don't stir. Cover with a glass lid or pressure cooker lid. If using the pressure cooker lid, be sure to turn the sealing valve to open. Turn on the "keep warm" setting. Gently stir the potatoes every 20 to 30 minutes to prevent them from sticking to the pot.

Step 5

When ready to serve, spoon into a serving dish and top with chopped chives and a few pats of butter.