Root Vegetable Mash

Ingredients

• 1/2 teaspoon salt, divided
• 2 tablespoons unsalted butter
• 3 cups peeled, cubed Yukon gold potatoes (about 2 large)
• 3 cups peeled, chopped celeriac (celery root)
• 1 1/2 cups chopped parsnips (about 2)
• 1/4 cup finely chopped onion
• 1 cup fat-free, less-sodium chicken broth
• 1/2 cup water
• 1 fresh thyme sprig
• 1/4 teaspoon freshly ground black pepper
• 1/4 cup half-and-half