Celeriac Cauli Mash

Ingredients

• 1 medium head of cauliflower (about 1 1/2 pound, cut into small florets)
• 2 pounds celery root (also known as celeriac (about 3 small))
• 2 cups radishes (roughly chopped)
• 3 cups sour cream (plain greek yogurt may be substituted)
• 1 1/2 cups broth (can be vegetable, or creature of choice)
• 1 teaspoon truffle powder
• 2 teaspoons kosher salt (plus more as needed)
• 1 teaspoon black pepper (freshly ground)
• 6 tablespoons grassfed salted butter (3/4 stick, at room temperature)
• 1/4 cup Parmesan cheese (shredded)
• Freshly ground white pepper