courtesy of Bon Appetit, Victoria Granof

This mash gets a punch of flavor from freshly grated horseradish. Use a combination of potato varieties to add more texture.



Ingredients
2 1/2 pounds mixed russet, Yukon Gold, and white-skinned potatoes, peeled, cut into 2\" cubes
1 1-pound celery root (celeriac), peeled, cut into 3/4\" cubes
1 6\" piece of horseradish, peeled, coarsely grated
1 1/2 cups sour cream
3 tablespoons Dijon mustard
2 tablespoons (1/4 stick) unsalted butter
Kosher salt


Method

1. Place potatoes, celery root, and horseradish in a large pot. Add water to cover by 1\". Bring to a boil, reduce heat to medium-high, and simmer until vegetables are tender, 25-30 minutes.
2. Drain, reserving 1 cup cooking liquid. Return vegetables to pot; add sour cream, Dijon mustard, and butter. Using a potato masher, coarsely mash vegetables. Add reserved cooking liquid by tablespoonfuls if mash is too stiff. Season to taste with salt.