4 tablespoons unsalted butter, at room temperature
¾ cup (or more) whole milk
3 tablespoons Dijon mustard
kosher salt and ground black pepper to taste
Instructions
In a large pot, cover potatoes in lightly salted water and bring to a boil over high heat. Lower heat and simmer potatoes for 20-25 minutes, until potatoes are soft when a knife pierces through. Drain potatoes and return them to the pot.
Roughly mash the potatoes with a potato masher or pastry blender. (I leave the skins on for a more rustic feel, but peel potatoes if desired.) Add ¾ cup milk, butter, mustard, salt, and pepper and continue to mash until you reach desired consistency. Add more milk a couple tablespoons at a time if necessary.