Arrange potatoes in microwave safe dish and cover tightly with plastic wrap. Cut a 1/2″ slit for a vent in the plastic wrap. Microwave on high for 10-12 minutes or until tender; transfer to a bowl. Microwave buttermilk in a microwave safe cup for 30 seconds.
Pour buttermilk and oil over potatoes; mash until mostly smooth. You want a few pebble sized chunks throughout. Stir in parsley, chives, tarragon and salt. Top with cracked pepper.