Potato and Celery Root Mash

Ingredients

• 1 pound celery root peeled cut into 3/4" cubes (celeriac)
• 3 tablespoons dijon mustard 
• 1  horseradish grated peeled
• 8 servings kosher salt 
• 2.5 pounds yukon gold potatoes mixed peeled cut into 2" cubes
• 1.5 cups cream sour
• 2 tablespoons butter unsalted ()

Equipment

• pot
• potato masher

Directions

1. Place potatoes, celery root,and horseradish in a largepot.
2. Add water to cover by 1".Bring to a boil, reduce heatto medium-high, and simmeruntil vegetables are tender,25-30 minutes.
3. Drain, reserving 1 cupcooking liquid. Returnvegetables to pot; add sourcream, Dijon mustard, andbutter. Using a potato masher,coarsely mash vegetables.
4. Add reserved cooking liquid bytablespoonfuls if mash is toostiff. Season to taste with salt.