Okay, I know what you’re thinking: how good can something with spaghetti squash be? Miracle of miracles, this gratin is absolutely delicious. Somehow the usually bland vegetal flavor of the squash amplifies the earthiness of the mushrooms in a totally unexpected way. This is very loosely based on a recipe by my friend Deborah Madison.
8 SERVINGS
1 |
3½- to 4-pound spaghetti squash |
1¼ |
pounds mixed mushrooms (portabello, crimini and button) |
|
About 4½ tablespoons butter |
2¾ |
teaspoons salt |
2 |
tablespoons minced shallots |
3 |
slices prosciutto, cut into thin slivers |
2 |
leeks |
1 |
cup crème fraîche |
1 |
cup heavy cream |
½ |
round loaf day-old sourdough |
¼ |
cup freshly grated Parmigiano-Reggiano (about 1 ounce) |
Heat the oven to 400 degrees. Cut the squash in half and remove the seeds. Place the squash cut side down in a roasting pan and add about ½ inch water. Bake until the squash is easily pierced with a knife, about 1 hour. Do not turn off the oven.
Wipe the mushrooms clean, trim any hard stems and cut them into thick slices. Heat 3 tablespoons of the butter in a large skillet over medium-high heat until the foam subsides and the butter turns a light hazelnut color. Add the mushrooms and sprinkle with ¾ teaspoon of the salt. Cover tightly and cook, tossing occasionally, until the mushrooms begin to glisten and give up their moisture, about 3 minutes. Remove the cover and add the shallots. Raise the heat to high and continue cooking, stirring constantly, until the mushrooms are richly aromatic and soft but not flaccid, about 3 minutes. Transfer the mushrooms to a bowl and set aside.
Reduce the heat to low and, without wiping out the pan, add the prosciutto. Cut away the dark green leaves of the leeks, then quarter them lengthwise, leaving them attached at the roots. Rinse thoroughly under cold running water and slice thinly crosswise. Add the leeks to the prosciutto and cover tightly. Let the prosciutto and leeks sweat slowly, stirring occasionally, until the leeks are quite tender, about 10 minutes.
Add the mushrooms back to the pan along with any liquid that has accumulated in the bottom of the bowl. Stir to combine with the prosciutto and leeks. Add the crème fraîche and continue to cook slowly, stirring occasionally, while you clean the squash.
Remove any scorched spots from the cut side of the squash. Hold 1 squash half over a large bowl and, using a fork, scrape out the strands, separating them as you work from one end of the squash to the other. When there is little left but the skin, empty the squash strands into the bowl. Repeat with the other half, adding the squash to the bowl. Season the squash with the remaining 2 teaspoons salt and stir well to combine.
Add the mushroom mixture to the squash and stir to combine. Transfer the mixture to a large gratin or baking dish, mounding it slightly in the center. Add the heavy cream, shaking the pan gently to distribute it through the squash. The cream should just be visible around the edge of the squash. Bake until the cream is bubbling and beginning to darken around the edge, about 15 minutes.
While the gratin is baking, prepare the bread crumbs. Cut away the crusts of the sourdough and cut the interior into cubes. Process in a blender to make coarse crumbs; you should have about 2½ cups. Add the cheese and pulse 3 or 4 times to thoroughly combine.
Scatter the bread crumbs evenly over the gratin, then dot with about 1½ tablespoons butter. Return to the oven and bake until the top is golden brown, about 15 minutes. Let cool slightly before serving.