This beautiful side dish from Bon Appetit is finished with crispy Jerusalem artichokes for extra crunch.
1-2 celery roots, trimmed, peeled and cut into 1-inch cubes
1-1½ pounds fingerling potatoes, peeled and cut into ¾-inch cubes
2 cups chicken broth or water
2 cups whole milk
3 garlic cloves, peeled
3 thyme sprigs
1 bay leaf
4 tablespoons unsalted butter
8 ounces Jerusalem artichokes, scrubbed
½ tablespoon olive oil
1 teaspoon chopped fresh thyme
1. Combine first 7 ingredients in heavy large pot. Add enough water to cover. Sprinkle with salt. Bring to boil, reduce heat to medium, and simmer with lid slightly ajar until vegetables are tender, 15 to 20 minutes.
2. Drain; return to pot. Discard thyme sprigs and bay leaf. Stir over medium heat to dry vegetables. Using potato masher, mash vegetables until coarsely pureed. Mash in 3 ½ tablespoons butter. Season with salt and pepper
3. Preheat oven to 425°. Cut Jerusalem artichokes into ½-inch cubes. Place in medium bowl; add oil, sprinkle with salt and pepper, and toss to coat. Dot with remaining ½ tablespoon butter. Transfer to rimmed baking sheet; roast until tender and golden brown, turning occasionally, about 25 minutes.
4. Place celery root and potato purée in serving bowl. Sprinkle Jerusalem artichokes and chopped thyme over and serve.