Mustard Mashed Potatoes

Bahan-bahan (6 porsi)

• 2¾ pounds medium sized Yukon Gold potatoes, (peeled and quartered)
• 6 tablespoons (¾ stick) salted butter, (at room temperature)
• ⅔ cup (or more) whole milk
• 3 tablespoons Dijon mustard
• kosher salt and freshly ground black pepper, (to taste)