Instant Pot pressure cooker - put a rack inside the pot. Add 1 cup water. Place washed and scrubbed potatoes on the rack. With a fork, poke each potato once. Close the lid. Press pressure cook and set time to 11 minutes for large potatoes. 8 minutes for medium/small potatoes. When timer is up, turn off unit and leave for 10 minutes. Release pressure, open lid and remove potatoes. Set them on a plate for a few minutes.
Heat up butter in a saucepan. Heat up milk separately.
Peel potatoes while still hot. Use gloves if necessary. Cut each potato in half or thirds to fit in ricer. Ricer should not be filled more than halfway. Place cut potatoes in ricer and press handles to squeeze out potatoes into a bowl.
Add melted butter to potatoes and mix with a fork. Add salt, black pepper and cream. Mix with a fork. Taste and adjust salt and pepper. Add more hot cream or milk to get the thickness you like.
Optional - add 1 tbsp of sour cream and mix in.
***To keep mashed potatoes warm - Turn on "saute" mode on Instant Pot. Fill the inner steel pot 1/3 with water. When water is very hot, place potatoes in a heat proof bowl and put on top of instant pot. Water should not touch bottom of bowl. Cover with a lid. If water is boiling rapidly, turn off Instant Pot. Turn on again if you need to keep the potatoes warm for a longer period of time. Stir potatoes before serving.