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1
Preheat oven to 350u00b0F.
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2
Coat a 9-by-13-inch baking dish with cooking spray.
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3
Bring a large pot of water to a boil. Cook noodles until not quite al dente, about 2 minutes less than the package directions. Drain; return the noodles to the pot and cover with cool water.
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4
Melt butter in a Dutch oven or large skillet over medium heat. Add leeks; cook, stirring often, until softened, about 6 minutes. Sprinkle flour over the leeks; stir well. Cook, stirring constantly, for 2 minutes. Whisk in milk in a slow stream and cook, whisking constantly, until thick and bubbling, 8 to 10 minutes. Whisk in thyme, salt, nutmeg and pepper. Remove from the heat.
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5
Assemble lasagna in the prepared baking dish by layering one-third of the noodles, one-third of the sauce, half the squash, one-third of the cheeses, half the remaining noodles, half the remaining sauce, all the pine nuts, all the remaining squash, half the remaining cheese, all the remaining noodles, all the remaining sauce and all the remaining cheese. Cover with parchment paper then foil.
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6
Bake the lasagna for 50 minutes. Uncover and bake until bubbling and lightly browned, 30 to 45 minutes more. Let stand for 10 minutes before serving (or follow make-ahead instructions).
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7
Make Ahead Tip:
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8
Bake, let cool for 1 hour, cover with parchment paper then foil and refrigerate for up to 3 days. Reheat, covered, at 350u00b0F for 1 hour, then uncovered for 30 minutes more.
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9
Tip:
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10
To toast pine nuts, cook in a small dry skillet over medium-low heat, stirring constantly, until fragrant and lightly browned, 2 to 4 minutes.
