- 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
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.