A generous quantity of cream and shredded Gruyère cheese turn sweet potatoes and butternut squash into a decadent side dish that’s elegant enough for a dinner party or the Thanksgiving table. But there’s no need to wait for a special occasion: A spiralizer makes quick work of cutting the vegetables, so you can make this dish any night of the week. Served with a green salad, it makes a satisfying fall vegetarian supper.
Spiralized Sweet Potato and Butternut Squash Gratin
1 Tbs. olive oil
1/2 cup (2 1/2 oz./75 g) finely chopped shallots
2 1/2 tsp. chopped fresh sage
2 cups (16 fl. oz./500 ml) heavy cream
2 tsp. kosher salt
1/4 tsp. freshly ground pepper
1 1/2 lb. (750 g) sweet potatoes, peeled and cut using the fine shredder blade of a Spiralizer
1 1/2 lb. (750 g) butternut squash, peeled and cut using the chipper blade of a Spiralizer
1 1/2 cups (6 oz./185 g) shredded Gruyère cheese
1/4 cup (1 oz./30 g) grated Parmesan cheese
2 Tbs. dried bread crumbs
Preheat an oven to 375°F (190°C). Butter a large gratin dish or a 13-by-9-inch (33-by-23-cm) baking dish.
In a saucepan over medium heat, warm the olive oil. Add the shallots and 2 tsp. of the sage and cook, stirring occasionally, for 3 minutes. Add the cream, salt and pepper and whisk until blended. Remove from the heat and let cool slightly.
In a large bowl, toss together the sweet potato and butternut squash. Pour the cream mixture over the potato mixture and toss to coat evenly.
In a small bowl, stir together the Gruyère and Parmesan cheese.
Arrange a layer of the sweet potato and butternut squash mixture in the prepared dish. Sprinkle with one-third of the cheese mixture. Repeat the layering twice more, ending with the cheese. Pour any remaining cream from the bowl over the gratin and top with the bread crumbs and the remaining 1/2 tsp. sage.
Cover the dish loosely with aluminum foil and bake for 45 minutes. Remove the foil and continue baking until the top is golden and the vegetables are tender when pierced, 30 to 45 minutes more. Let stand for 10 minutes before serving. Serves 8 to 10.
Williams-Sonoma Test Kitchen