Peel and quarter the potatoes, place them in a large pot, and cover with water. Bring to a boil over medium-high heat and cook until the potatoes are tender, about 20 minutes.
Meanwhile, heat the butter in a medium saucepan over medium-low heat. Once melted, add the sage leaves and cook until the butter begins to brown, about 3-4 minutes. Remove the sage leaves and
Add the milk to the butter and bring them to a simmer. Turn off the heat and set aside.
Once the potatoes are cooked through, drain well. Mash the potatoes with a potato masher. Add the butter-cream mixture, Parmesan, and salt. Keep mashing until its smooth and no lumps remain.
Transfer the mashed potatoes to a serving platter, drizzle with the remaining butter, and garnish with finely chopped sage.