Celeriac & Parsnip Mash
1 medium celeriac, (about 1 pound), peeled and cut into 1-inch cubes
3 medium parsnips, (about 3/4 pound), peeled and cut into 1-inch slices, thick ends quartered
1 large russet potato, (about 3/4 pound), peeled and quartered
1/4 cup vegetable broth, or reduced-sodium chicken broth
2 tablespoons extra-virgin olive oil
3 tablespoons chopped fresh chives, divided
2 tablespoons low-fat or nonfat plain yogurt
1 ½ teaspoons Dijon mustard
½ teaspoon salt
½ cup freshly grated Parmesan cheese
Freshly ground pepper, to taste
Place celeriac and parsnips in a large saucepan; cover with lightly salted water.
Place potato in a medium saucepan; cover with lightly salted water. Bring both saucepans to a boil over medium-high heat. Reduce heat to low, cover, and simmer gently until the vegetables are very tender when pierced with a fork, about 20 minutes for the potato and 30 to 40 minutes for the celeriac and parsnips.
When the potato is tender, drain and transfer to a large bowl. Mash with a potato masher. Cover and keep warm. When the celeriac and parsnips are tender, drain and transfer to a food processor; process until smooth, stopping once or twice to scrape down the sides. Add the puree to the potato.
Meanwhile, combine broth and oil in a saucepan (or measuring cup) and heat on the stovetop (or in the microwave) until steaming. Stir into the puree, along with 2 tablespoons chives, yogurt, mustard, salt and pepper. Stir in Parmesan. Garnish with the remaining 1 tablespoon chives. Serve hot.