Wash potatoes and add to Instant Pot on rack with 1 cup of water in the bowl. Cook on high pressure 14 minutes and quick release. Check potatoes for doneness with a fork. Add minutes until potatoes are cooked through. Melt butter in bowl and rice potatoes with the butter. Mix butter into the potatoes. Add sour cream, chives and salt and microwave for about a minute to warm. Add ¾ cup parmesan and microwave 1 to 2 minutes until parmesan is melted. Add potatos to a baking dish and add remaining Parmesan cheese to top of potatoes. Broil under low broil for 1 to 2 minutes until cheese is melted and slightly browned.