BUTTERNUT SQUASH AND POTATO GRATIN WITH FRESH SAGE

Butternut Squash and Potato Gratin with Fresh Sage image

Yield SERVES 4 TO 6

Number Of Ingredients 9

2 tablespoons unsalted butter, plus more for the pan
1 large shallot, minced
1 1/4 cups heavy cream
5 large sprigs fresh thyme, leaves chopped
12 large sage leaves
Kosher salt and freshly ground black pepper
3 medium russet or Yukon gold potatoes (about 1 1/2 pounds), peeled and sliced into 1/8-inch thick rounds
1/4 small butternut squash (preferably from the stem end), peeled and sliced 1/8 inch thick
1 cup grated Parmigiano-Reggiano cheese

Steps:

Position a rack in the center of the oven and heat to 350°F.
Melt the butter in a small saucepan over medium heat. Add the shallot and cook, stirring, until it softens and becomes translucent, about 30 seconds. Add the cream, thyme, 5 of the sage leaves, 2 teaspoons salt, and a few grinds of pepper and bring to a boil. Remove from the heat and let the sage infuse in the cream for 10 minutes. Then remove and discard the sage leaves.
Generously butter an 8 by 8-inch baking dish and arrange one-third of the potatoes and one-third of the squash across the bottom, overlapping them slightly to make a relatively even layer. Pour one-third of the cream mixture over the potatoes and sprinkle with one-third of the cheese. Build 2 more layers in the same way; on the last layer, add the remaining potatoes and cream, then arrange the remaining 7 sage leaves decoratively over the top. Finally, sprinkle on the remaining cheese.
Cover the dish with foil and bake for 30 minutes. Then remove the foil and continue baking until the top is golden and a skewer goes into the potatoes with no resistance, about 30 minutes longer.
Let rest for about 10 minutes before serving.