Step 1

Set a rack in the bottom of a 6-quart Instant Pot® and add 3 cups water. Stack the potatoes on the rack. Follow the manufacturer's guide for locking the lid and preparing to cook. Set to pressure cook on high for 15 minutes.

Step 2

After the pressure-cook cycle is complete, turn off the heat and let the steam release naturally for 20 minutes. After 20 minutes, follow the manufacturer's guide for steam release and allow any residual steam to air out. Being careful of any remaining steam, unlock and remove the lid; transfer the potatoes to a large bowl. Add the half-and-half, butter, sour cream and a large pinch of salt and pepper. Mash with a potato masher until desired texture and smoothness. Season with additional salt and pepper if needed.