This is a great dish to prepare ahead. The assembled gratin can be refrigerated overnight; to keep the nuts from getting soft, sprinkle them on just before serving. You can transport this gratin in an insulated carrier and serve it hot, but it’s also terrific served at room temperature.
Makes eight to 12 servings
Prep time: 30 minutes
Cook time: 90 minutes
- 2 1/2 lb. sweet potatoes, peeled
- 1 large celery root (2 lb.), peeled with a sharp knife and halved lengthwise
- 1 medium rutabaga (2 lb.), peeled and halved lengthwise
- 1/2 tbs. unsalted butter, melted, plus more for the pan
- Kosher salt
- Freshly ground black pepper
- 1 cup chicken or vegetable broth
- 1/4 cup heavy cream
- 1 1/2 cup walnuts
- 1 tsp. roughly chopped fresh thyme leaves
Using a mandoline or a sharp knife, slice the potatoes lengthwise into slabs that are about 1⁄8-inch thick. Halve the celery root and the rutabaga, and slice each into 1⁄8-inch-thick slabs, as well.
Preheat the oven to 375 degrees F. Butter a 9-x-13-inch glass or ceramic baking dish. Arrange one-third of the sweet potatoes in the dish, overlapping them slightly; season with salt and pepper. Top with half the rutabaga and then half the celery root, seasoning each layer.
Repeat the layering, ending with a third layer of sweet potatoes. Pour the broth over and around the vegetables. Cover the baking dish tightly with aluminum foil.
Bake for about 45 minutes, until the vegetables feel almost tender when pierced. Pour the cream over the gratin. Bake for 30 minutes, until the liquid has thickened.
Meanwhile, spread the walnuts on a baking sheet and toast in the oven for about four minutes, until fragrant. Let cool, and then coarsely chop. Return the chopped walnuts to the baking sheet, toss with the 1/2 tablespoon of butter and the thyme, and season with salt and pepper. Toast the nuts until nicely browned, about two minutes.
Remove the gratin from the oven and top with the walnuts. Let stand for 10 minutes. Serve hot, warm, or at room temperature.
Recipes reprinted from Modern Potluck: Beautiful Food to Share. Copyright © 2016 by Kristin Donnelly. Photography copyright © 2016 by Yossy Arefi. Published by Clarkson Potter / Publishers, an imprint of the Crown Publishing Group, a division of Penguin Random House LLC.
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