Add whole potatoes, enough water to cover them halfway, and 1 teaspoon salt to the Instant Pot.
Close the lid with the valve in the 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 multi-cooker.
If desired, you can slip the skins off 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.
Readjust the seasoning with the remaining salt and black pepper.
Garnish with fresh herbs if desired.