Ingredients

  • 4 pounds Idaho russet potatoes (about 5 potatoes), peeled and cut into 1-inch pieces
  • 1 pound celery root, peeled and cut into 1/2-inch pieces
  • Kosher salt
  • 2 sticks butter, 1 softened and 1 melted, plus more for greasing
  • 6 ounces cream cheese
  • 1 cup half-and-half, warmed
  • 1/4 cup prepared horseradish
  • 1 teaspoon garlic powder
  • 1/2 teaspoon ground white pepper
  • 1/4 cup fresh minced chives

Method

  • Add the potatoes, celery root and 1 tablespoon salt to a large saucepan and cover with water.
  • Bring to a boil and cook over medium-high heat until fork tender, about 15 minutes.
  • Drain the potatoes and celery root.
  • Preheat the oven to 350 degrees F. Grease a 9-by-13-inch baking pan.
  • Whip together the cream cheese and softened butter in a large bowl with a hand mixer on medium speed until thoroughly blended, about 2 minutes.
  • Add the hot potatoes and celery root slowly, alternating with the half-and-half.
  • Whip until blended.
  • Sprinkle with salt and stir in the horseradish, garlic powder and white pepper.
  • Pour the potato mixture into the prepared baking pan.
  • Pour the melted butter over the potato mixture.
  • Bake until bubbly and slightly brown, about 45 minutes.
  • Garnish with the chives.