Preheat oven to 225°

Place potatoes in saucepan covered by 2" cold water. Bring to boil over medium heat. Boil 25 minutes or until potatoes are tender.

Drain and spread potatoes on parchment lined baking sheet and bake for 15 minutes.

Bring milk and butter to simmer over medium heat. Do not boil.

Transfer potatoes to a large bowl. Add hot milk mixture and mash with a potato masher.

Slowly add buttermilk while mashing to desired consistency.

Add salt and pepper to taste.