Bring a pot of salted water to a boil and add the potatoes. Let them cook until tender, about 10-15 minutes depending on how thin you cut the potatoes. Drain once cooked through
While the potatoes are cooking in a small saucepan heat up the butter, buttermilk, whole milk, and fresh tarragon over medium high heat
Once the liquid comes to a simmer turn off the heat and let the tarragon steep in the milk
Mash the potatoes however you like… some people like them completely smooth while some like them a little chunky
Add half of the liquid (not the leaves) into the potatoes and mix together. Keep adding as much as you’d like until you get your desired consistency
Season well with salt and pepper and serve!