Place them into the Instant Pot and add 1 cup of water on top. Close the lid, make sure the knob is on sealing, and cook on "MANUAL" for 10 minutes.
When it is finished cooking, move the valve on the top of the lid to "VENTING" and do a quick release of all the pressure.
Drain the water from the pot.
Add sour cream, milk, salt, pepper, and Italian seasoning to warm potatoes.
Using a potato masher or a hand mixer (depending if you like them chunky or smooth), mash potatoes until they reach the consistency you desire.
Add more salt and pepper and other seasonings as needed.
Serve and enjoy!
Notes
The secret to making potatoes creamy depends on how much starch there is in your potato, so stick to the starchy potatoes like the Russet potatoes.
The other trick to making mashed potatoes creamy is that you need to smash the potatoes while they are still hot. I like to whip mine with an electric mixer, but a potato masher works great as well!