Portobello Mushroom Lasagna Recipe

Portobello Mushroom Lasagna is a luxurious “white lasagna” made with meaty slices of portobello mushrooms, fresh lasagna sheets, and a rich, velvety Béchamel sauce spiced with nutmeg and black pepper. Unlike traditional tomato-based versions, this dish relies on the earthiness of the mushrooms and the nutty saltiness of Parmesan cheese to create a deeply savory, sophisticated vegetarian main course. It is the ultimate comforting dinner for a cold night, offering a creamy decadence that satisfies even the biggest meat-eaters.

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Portobello Mushroom Lasagna Ingredients

For the Pasta and Mushrooms:

• 3/4 pound Dried Lasagna Noodles: Cooked al dente.
• 1 1/2 pounds Portobello Mushrooms: Stems discarded, caps wiped clean and sliced 1/4-inch thick. These provide a steak-like texture.
• Good Olive Oil: For boiling water and sautéing.
• 4 tablespoons (1/2 stick) Unsalted Butter: Divided, for sautéing mushrooms.
• 1 cup Freshly Ground Parmesan: Divided for layers and topping.
• Kosher Salt: To taste.

For the White Sauce (Béchamel):

• 4 cups Whole Milk: Warmed. Whole milk is essential for the creamy texture.
• 8 tablespoons (1 stick) Unsalted Butter: For the roux.
• 1/2 cup All-Purpose Flour: Thickening agent.
• 1 teaspoon Freshly Ground Black Pepper: Provides a sharp contrast to the cream.
• 1 teaspoon Ground Nutmeg: The signature spice that gives the white sauce its depth.
• 1 tablespoon Kosher Salt: Seasoning for the sauce.

How To Make Portobello Mushroom Lasagna

1. Boil the noodles: Preheat the oven to 375°F (190°C). Bring a large pot of water to a boil with 1 tablespoon of salt and a splash of olive oil (to prevent sticking). Add the lasagna noodles and cook for 10 minutes, stirring occasionally. Drain well and set aside.
2. Make the roux: Bring the milk to a simmer in a saucepan and set aside. In a large saucepan, melt 8 tablespoons (1 stick) of butter. Add the flour and cook over low heat for 1 minute, stirring constantly with a wooden spoon, to cook out the raw flour taste.
3. Thicken the sauce: Pour the hot milk into the butter-flour mixture all at once. Add 1 tablespoon salt, the pepper, and the nutmeg. Cook over medium-low heat, stirring constantly (switch to a whisk if lumps form), for 3 to 5 minutes until the sauce is thick and smooth. Remove from heat.
4. Sauté the mushrooms: Remove stems from the mushrooms and slice the caps. In a large (12-inch) sauté pan, heat 2 tablespoons of oil and 2 tablespoons of butter. When melted, add half the mushrooms. Sprinkle with salt and cook over medium heat for about 5 minutes until tender and releasing juices. Transfer to a bowl. Repeat with the remaining oil, butter, and mushrooms.
5. Assemble the layers: Spread a thin layer of white sauce in the bottom of an 8x12x2-inch baking dish. Arrange a layer of noodles on top. Spread with more sauce, then top with 1/3 of the cooked mushrooms and 1/4 cup of grated Parmesan.
6. Repeat the process: Repeat the layering (noodles, sauce, mushrooms, Parmesan) two more times. Finish with a final layer of noodles, the remaining white sauce, and the remaining Parmesan cheese sprinkled generously over the top.
7. Bake the lasagna: Place the dish in the preheated oven. Bake for 45 minutes, or until the top is browned and the sauce is bubbling and hot.
8. Serve the dish: Remove from the oven and allow the lasagna to sit at room temperature for 15 minutes. This resting time is crucial for the sauce to set so it cuts into clean squares. Serve hot.

Recipe Tips

• Mushroom Prep: Portobello mushrooms have dark gills underneath the cap. While edible, they can turn a white sauce a murky grey color. For a pristine white lasagna, gently scrape the gills out with a spoon before slicing.
• Batch Cooking: Do not crowd the mushrooms in the pan. Cooking them in two batches ensures they sear and brown rather than steam, concentrating their earthy flavor.
• Hot Milk: Using hot milk when making the white sauce (Béchamel) helps it thicken instantly and reduces the chance of lumps forming compared to using cold milk.
• Resting Time: As with all lasagnas, if you cut into it immediately out of the oven, the layers will slide apart. The 15-minute rest allows the Béchamel to firm up.

What To Serve With Portobello Lasagna?

This is a rich, heavy dish that needs acidity to cut through the dairy. A crisp green salad with a sharp lemon vinaigrette or balsamic dressing is the perfect partner. A side of garlic bread is excellent for mopping up any extra white sauce. For wine, a rich, oaked Chardonnay complements the buttery mushrooms and nutmeg beautifully.

How To Store Leftovers Portobello Lasagna?

• Refrigerate: Cover the baking dish tightly with foil or transfer slices to an airtight container. Store in the refrigerator for up to 3 days.
• Reheat: Reheat individual slices in the microwave, or warm the whole covered dish in a 350°F oven for 20 minutes. You may need to add a splash of water if the sauce has thickened too much.
• Freeze: White sauce can sometimes separate when frozen, but lasagna generally holds up well. Freeze baked or unbaked portions for up to 2 months. Thaw in the fridge overnight before baking.

Portobello Mushroom Lasagna Nutrition Facts

• Calories: ~650 kcal
• Fat: 40g
• Carbohydrates: 55g
• Protein: 22g
• Nutrition information is estimated per serving based on 6 servings.

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