Polenta Lasagna with Mushrooms

Ingredients:

Sauce

• 45 g dried porcini mushrooms, rinsed
• 3 tablespoons unsalted butter
• 3 tablespoons extra-virgin olive oil
• 450 g of champignons, cut into 4 pieces
• 450 g shiitake mushrooms, quartered (stems removed)
• 1 small onion, chopped
• 2 cloves garlic, crushed
• 1/4 tsp red pepper flakes
• 3 tbsp tomato paste
• 1 can (425g) canned whole San Marzano tomatoes, broken up by hand
• 0.5 cup chopped fresh parsley + extra for serving

Lasagna

• 2.5 cups quick-cooking polenta
• 1 cup grated Parmesan (about 100 g)
• 2 large eggs, lightly beaten
• 1/4 teaspoon freshly grated nutmeg
• Extra-virgin olive oil to grease the pan
• 3 cups grated semi-skimmed mozzarella

Preparation:

1. Soak dried porcini mushrooms in 3 cups of hot water for 30 minutes. Remove the mushrooms, reserving 2 cups of the liquid. Coarsely chop the porcini mushrooms.
2. Prepare the sauce:
   
   In a large saucepan or Dutch oven, heat 1 tablespoon each of butter and olive oil over medium-high heat. Add half of the mushrooms and shiitake mushrooms and cook, undisturbed, until lightly browned on the bottom, about 2 minutes. Continue cooking, stirring, until softened, another 2 to 3 minutes; transfer the mushrooms to a bowl. Add another 1 tablespoon each of butter and olive oil, the remaining mushrooms and shiitake mushrooms, and cook in the same manner. Transfer to a bowl and add 1/2 teaspoon of salt.
3. Reduce heat to medium and add another 1 tablespoon each of butter and olive oil to the pan. Add the onion and porcini mushrooms and cook, stirring, until the onion is soft, about 4 minutes. Add the garlic and red pepper flakes. Add the tomato paste and cook, stirring, until darkened, 1 to 2 minutes. Add 2 cups of the porcini mushroom liquid, the pureed tomatoes, the fried mushrooms, and 1/2 teaspoon of salt. Bring to a simmer and cook, stirring occasionally, until the sauce thickens, about 30 minutes. Remove from heat and stir in the parsley; season with salt to taste.
4. Make lasagna:
   
   Bring 7 cups of water to a boil in a large saucepan; transfer to a large heatproof bowl. Meanwhile, bring 3 cups of water to a boil in another large saucepan. Gradually whisk in the polenta and 1.5 teaspoons of salt. Cover the bowl tightly with foil and set it over the saucepan of simmering water. Reduce the heat to a gentle simmer; cook the polenta until the liquid is absorbed, about 15 minutes. Remove from the heat, uncover, and vigorously stir in the Parmesan, eggs, and nutmeg.
5. Preheat oven to 350°F (175°C). Lightly grease a 3-quart (3-liter) baking dish with olive oil. Place a third of the polenta on a serving platter and top with half the mushroom sauce. Sprinkle with 1 cup of mozzarella. Repeat the layers (polenta, sauce, mozzarella), then top with the remaining polenta. If the polenta becomes too thick, add a little hot water.
6. Cover the pan loosely with foil and bake until bubbly, 50 minutes to 1 hour. Turn the oven to broil. Uncover the lasagna and sprinkle the remaining 1 cup mozzarella on top; broil until the cheese is melted, 2 to 3 minutes. Sprinkle with parsley. Let stand for 15 minutes and serve.