4 Tablespoons unsalted butter
1 Tablespoon chopped fresh rosemary
1¾ pounds russet potatoes, peeled and cut into 1-inch cubes
1 teaspoon salt
½ cup warm milk
2 ounces Parmesan cheese, freshly grated (½ cup)
Freshly ground pepper
Melt butter in a small saucepan. Add rosemary and set aside. Place potatoes in a medium saucepan. Cover with cold water and add salt. Boil over medium-high heat until tender, about 15 minutes. Drain. Transfer to a large bowl. Add milk and mash with a potato masher. Add Parmesan and rosemary butter. Mix with an electric mixer until smooth. Season with salt and pepper. Serves 4 to 6.