For the best results, use a variety of mushrooms. I used equal parts shiitake, crimini, and trumpet mushrooms. If working with shiitake mushrooms, remove the tough, fibrous stems before slicing.
3/4 pound dried lasagna noodles
4 cups whole milk
12 tablespoons (1 1/2 sticks) unsalted butter, divided
1/2 cup all-purpose flour
1 teaspoon black pepper, freshly ground
1 teaspoon nutmeg, freshly grated
3 tablespoons extra-virgin olive oil, divided
1 large leek, thinly sliced and cleaned 
1 1/2 pounds mushrooms
1 1/2 cups parmesan, freshly grated
- Preheat the oven to 375°F.
- Bring a large pot of generously salted water to a boil. Add the lasagna noodles and cook according to the package's instructions, stirring occasionally. Drain and separate the noodles, laying them out on parchment or wax paper so that they don't stick together.
- Heat the milk to just below a simmer in a saucepan; set aside. Melt 8 tablespoons (1 stick) of the butter in a large saucepan. Add the flour and cook for 1 minute over low heat, stirring constantly with a wooden spoon. Pour the hot milk into the butter-flour mixture all at once. Add 1 tablespoon salt, the pepper, and nutmeg, and cook over medium-low heat, stirring first with the wooden spoon and then with a whisk, for 3 to 5 minutes, until thick. Take off the heat and press a piece of parchment paper over the surface of the sauce to avoid a skin from forming.
- Add 1 tablespoon butter and 1 tablespoon olive oil to a large sauté pan or dutch oven and cook over medium heat. When the butter melts, add the leeks, sprinkle with salt, and cook, stirring occasionally, until tender and beginning to brown, about 10 minutes. Transfer to a large heat-safe bowl.
- Slice the mushrooms 1/4-inch thick. Add 1 1/2 tablespoons butter and 1 tablespoon olive to the same pan as the leeks were cooked in; cook over medium heat. When the butter melts, add half the mushrooms, sprinkle with salt, and cook for about 5 to 7 minutes, or until the mushrooms are tender, they release some of their juices, and are beginning to brown. If they become too dry, add a little more oil. Toss occasionally to make sure the mushrooms cook evenly. Add to the bowl with the leeks. Repeat with the remaining mushrooms (adding 1 1/2 tablespoons of butter and 1 tablespoon of oil to the pan as before). Add to the bowl with the leeks.
- To assemble the lasagna, spread about 1/4 of the sauce in the bottom of an 8-by-12 by 2-inch baking dish. Arrange a layer of noodles on top, then 1/4 of the sauce, then 1/3 of the mushroom-leek mixture, and a heaping 1/4 cup grated parmesan. Repeat 2 more times, layering noodles, sauce, mushroom-leek mixture, and parmesan. Top with a final layer of noodles and sauce, and sprinkle with the remaining parmesan.
- Bake the lasagna for 45 to 55 minutes, or until the top is browned and the sauce is bubbly and hot. Allow to sit at room temperature for 15 minutes before slicing; serve hot.
- Pasta, Main Dishes
- 6-8 servings