Add whole potatoes and 1 teaspoon salt to Instant Pot and enough water to cover them halfway. Close the lid with the valve in sealing position, select Manual mode, and adjust the cooking time to 20 minutes under high pressure. After the cooking time is up, allow pressure to release naturally for 10 minutes before opening the lid. Drain the potatoes, and add them back into the Instant Pot. If desired, you can slip the skins off of the potatoes at this point. Add the milk, sour cream, butter, 3/4 of the goat cheese, and any optional fresh herbs, then mash well with a potato masher until smooth.