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1
Preheat oven to 350F.
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2
Spray a 9-by-13-inch baking dish with nonstick cooking spray or greased with butter
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3
Bring a large pot of water to a boil.
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4
Cook noodles until not quite al dente, about 2 minutes less than the package directions.
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5
Drain, return the noodles to the pot and cover with cool water.
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6
Heat butter and oil in a Dutch oven over medium heat.
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7
Stir in leeks, cook, stirring often, until softened, 5 to 8 minutes.
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8
Sprinkle flour over the leeks, mix well.
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9
Cook, stirring often, for 2 minutes.
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10
Pour in milk in a slow stream and cook, whisking constantly, until thick and bubbling, about 9 minutes.
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11
Stir in in thyme, salt, nutmeg and pepper.
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12
Remove from the heat.
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13
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 cheese, 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.
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14
Cover with parchment paper then foil.
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15
Bake the lasagna for 50 minutes.
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16
Uncover and bake until bubbling and lightly browned, 40 to 45 minutes more.
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17
Allow to cool for a few minutes.
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18
Serve warm.
