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1
Make the sauce: Soak the dried porcini in 3 cups hot water, 30 minutes.
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2
Drain, reserving 2 cups of the soaking liquid.
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3
Roughly chop the porcini.
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4
Heat 1 tablespoon each butter and olive oil in a large pot or Dutch oven over medium-high heat.
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5
Add half of the button and shiitake mushrooms and cook, undisturbed, until slightly browned on the bottom, about 2 minutes.
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6
Continue to cook, stirring, until soft, 2 to 3 more minutes; transfer to a bowl.
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7
Repeat with another 1 tablespoon each butter and olive oil and the remaining button and shiitake mushrooms.
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8
Transfer to the bowl and add 1/2 teaspoon salt.
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9
Reduce the heat to medium and add the remaining 1 tablespoon each butter and olive oil to the skillet.
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10
Add the onion and porcini and cook, stirring, until the onion is soft, about 4 minutes.
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11
Stir in the garlic and red pepper flakes.
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12
Add the tomato paste and cook, stirring, until darkened, 1 to 2 minutes.
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13
Add the reserved 2 cups porcini liquid, the crushed tomatoes, button and shiitake mushrooms and 1/2 teaspoon salt.
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14
Bring to a simmer and cook, stirring occasionally, until thickened, about 30 minutes.
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15
Remove from the heat and stir in the parsley; season with salt.
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16
Prepare the lasagna: Bring 7 cups water to a boil in a large saucepan; transfer to a large heatproof bowl.
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17
Meanwhile, bring 3 cups water to a boil in a separate large saucepan.
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18
Gradually whisk the polenta and 1 1/2 teaspoons salt into the bowl of hot water.
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19
Cover the bowl tightly with foil and set over the saucepan of boiling water.
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20
Reduce the heat so the water is simmering; cook the polenta until the liquid is absorbed, about 15 minutes.
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21
Remove from the heat, uncover and vigorously whisk in the parmesan, eggs and nutmeg.
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22
Preheat the oven to 350 degrees F. Lightly brush a 3-quart baking dish with olive oil.
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23
Spread one-third of the polenta in the dish and top with half of the mushroom sauce.
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24
Sprinkle with 1 cup mozzarella.
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25
Repeat the layers (polenta, sauce, mozzarella), then top with the remaining polenta.
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26
(If the polenta gets too thick, whisk in a little hot water.)
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27
Loosely cover the dish with foil and bake until bubbly, 50 minutes to 1 hour.
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28
Turn on the broiler.
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29
Uncover the lasagna and top with the remaining 1 cup mozzarella; broil until melted, 2 to 3 minutes.
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30
Sprinkle with parsley.
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31
Let stand 15 minutes before serving.
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32
Photograph by Con Poulos
