The key to perfect, fluffy spuds is not overworking them with an electric mixer; a ricer (or food mill, if you have one) or potato masher is the best tool for the job.
2 pounds baking potatoes, peeled and cut into 1-inch pieces
1 pound cubed peeled turnip
2/3 cup warm half-and-half
1 tablespoon butter, melted
1 1/4 teaspoons kosher salt
1/2 teaspoon freshly ground black pepper
1 tablespoon butter
2 cups chopped leek
How to Make It
Place potatoes in a large saucepan; cover with water. Bring to a boil; reduce heat, and simmer 15 minutes or until tender. Drain. Press potatoes through a ricer back into pan, or mash with a potato masher to desired consistency.
Add half-and-half, 1 tablespoon melted butter, kosher salt, and black pepper; stir well. Melt 1 tablespoon butter in a medium skillet over medium heat. Add leek; cook 4 minutes or until tender, stirring frequently. Stir into potatoes.