This is my sister-in-law's recipe and she said I could share. According to her, they are the best ever! AND she figured out how to duplicate. Why such a big deal about mashed potatoes? HEY! They are the ultimate comfort food...warm, buttery, soft and fluffy...get the picture?!!
Cafeteria (NYC) Mashed Potatoes
2 1/2 pounds potatoes (red-skinned, about 6 to 7 potatoes)
Optional: 3 to 4 cloves garlic (personally, I don't think that it's optional...giggle...)
1 tsp kosher salt, plus more to taste if required
1 cup water or low sodium chicken stock, or low-sodium vegetable broth
1/2 cup half-and-half or whole milk
3 tbs butter
Black pepper to taste
Optional: fresh chopped parsley
Optional: fresh chopped chives
(Personally, I don't think that either of these herbs are optional...just my opinion...)
Scrub the potatoes and remove any eyes or imperfections. If desired, peel the potatoes. Cut into 1-inch to 2-inch cubes. Put the potatoes in the Instant Pot.
If adding garlic, peel the cloves and mince.
Add the salt to the potatoes along with the water or stock.
Cover the pot and make sure the vent is set​ to "seal."
Cook on high pressure for 8 min and then quick release.

Meanwhile, on the stovetop or in the microwave, heat the half-and-half or milk with the butter until hot and the butter has melted.
Place a large sieve or colander over a bowl and drain the potatoes and garlic. Reserve the cooking liquid in the bowl and set aside.
Put the potatoes and garlic in a large bowl and mash with a potato masher to break up.
Add the hot milk or cream and butter mixture and continue mashing until the potatoes are smooth and creamy. Add some of the cooking liquid to the potatoes to reach desired consistency.
Taste and add salt and freshly ground black pepper, to taste.
Spoon the mashed potatoes into a serving bowl and sprinkle with fresh chopped parsley, if desired. Serves 4-6