Preparation Brush an 8x8x2" or other 6-cup baking dish with 1 tablespoon melted butter. Place potatoes in a large pot and add cold water to cover by 1". Add a large pinch of salt; bring to a boil, then reduce heat to medium-low. Cover with lid slightly ajar and gently simmer until potatoes are tender, about 20 minutes. Drain potatoes; return to same pot. Shake and stir with a wooden spoon over very low heat until dry. Then, using a potato masher, mash coarsely. Using a hand mixer, beat 1/2 cup butter into potatoes, a few pieces at a time, until blended. Beat in cream cheese, adding a few pieces at a time, then horseradish. With motor running, gradually add milk, beating until potatoes are light and fluffy, 4-5 minutes. Season well with salt and pepper. Stir in scallions. Scrape potatoes into prepared dish.3 Use a spatula to create peaks across the surface. Drizzle potatoes with remaining 1 tablespoon melted butter and sprinkle with paprika. DO AHEAD: Potatoes can be made 1 day ahead. Let stand at room temperature to cool. Cover and chill. Preheat oven to 350°F. Bake potatoes, uncovered, until they are heated through and top is golden, about 40 minutes (if chilled, add 10 minutes).
Preparation Brush an 8x8x2" or other 6-cup baking dish with 1 tablespoon melted butter. Place potatoes in a large pot and add cold water to cover by 1". Add a large pinch of salt; bring to a boil, then reduce heat to medium-low. Cover with lid slightly ajar and gently simmer until potatoes are tender, about 20 minutes. Drain potatoes; return to same pot. Shake and stir with a wooden spoon over very low heat until dry. Then, using a potato masher, mash coarsely. Using a hand mixer, beat 1/2 cup butter into potatoes, a few pieces at a time, until blended. Beat in cream cheese, adding a few pieces at a time, then horseradish. With motor running, gradually add milk, beating until potatoes are light and fluffy, 4-5 minutes. Season well with salt and pepper. Stir in scallions. Scrape potatoes into prepared dish.3 Use a spatula to create peaks across the surface. Drizzle potatoes with remaining 1 tablespoon melted butter and sprinkle with paprika. DO AHEAD: Potatoes can be made 1 day ahead. Let stand at room temperature to cool. Cover and chill. Preheat oven to 350°F. Bake potatoes, uncovered, until they are heated through and top is golden, about 40 minutes (if chilled, add 10 minutes).