Mashed Potato & Roots Casserole

Place potatoes, rutabaga (and/or celeriac) and garlic in a large pot. Cover with water. Cover and bring to a boil over high heat. Adjust heat to maintain a lively simmer. Cook until the vegetables are tender, about 15 minutes.

Meanwhile, preheat oven to 350°F. Coat a 9-by-13-inch baking dish with cooking spray.

Drain the vegetables and return to the pot; mash with a potato masher. Add cream cheese, yogurt, milk, 1 tablespoon thyme, salt and pepper; mash until evenly incorporated. Scrape into the prepared baking dish. Sprinkle with the remaining 2 teaspoons thyme.

Bake until golden brown on top, 1 to 1 1/4 hours. Let stand for 15 minutes before serving.