Wash and peel 2lbs of Russet potatoes (about 7 medium potatoes). Once peeled, place into a bowl of water so potatoes do not brown.
Place wire rack inside of a 6qt Instant Pot and place whole potatoes on top of the rack. Cover with 1 1/2 cups of chicken or vegetable stock.
Close the lid to the Instant Pot and set vent to sealing. Set the Instant Pot to 20 minutes on Manual (high pressure). (The Instant Pot will take 10-15 minutes to come up to pressure before counting down).
Once the Instant Pot counts down and beeps, let it set for 15 minutes of natural release. After 15 minutes, quick release any pressure that is left before opening the lid.
Open the lid, remove the potatoes and wire rack and dispose of the remaining stock in the pot. Return potatoes back to the pot.
Using a hand masher, lightly mash the potatoes. Add butter to the lightly mashed potatoes and fold in using a spoon or spatula. Then mash potatoes again to desired consistency.
Heat milk and salt in the microwave for a minute. Add milk mixture to the potatoes slowly, making sure it is absorbed completely.
At this point taste the potatoes and add salt and pepper to taste. Top with additional butter and chives for garnish.