Butternut Squash Lasagna with Walnuts and Sage

Lasagna is a labor of love. If I’m going to put in the effort, I want a spectacular result, and my standards are just as high when it comes to vegetarian versions of this Italian-American favorite.
This sophisticated butternut squash lasagna proves it’s possible to achieve delicious results without too much fuss. It’s a simple filling of sliced butternut squash, sautéed shallots, walnuts, and fresh sage that delivers lots of savory flavor. To make what is traditionally a heavy dish lighter, I make a rich and creamy béchamel using low-fat milk and olive oil instead of butter. A few key ingredients and techniques help keep the prep time reasonable with excellent results.

This butternut squash lasagna recipe is easy enough to make on a relaxed Sunday afternoon for your family, and elegant enough to serve to company.

Butternut Squash Lasagna Ingredients 

This elegant dish is made with simple ingredients available at any well-stocked grocery store. Here is what you’ll need:

For the Filling

• Butternut squash: Rich, nutty, and dense, this bright-orange squash is the star ingredient. It’s also perfectly suited to baking, becoming tender and sweeter as it cooks.
• Extra virgin olive oil: Since this dish is already rich, we use just a tablespoon to sauté the filling ingredients.
• Shallots: A generous amount of sauteed shallots gives this recipe its savory flavor. You can also use an equal amount of sliced red onion.
• Walnuts may seem like an unusual ingredient in lasagna, but they serve an important purpose! Besides adding richness and earthy flavor, they provide a crunchy contrast to the tender squash and noodles.
• Sage: Woodsy and peppery, sage makes this dish taste like cozy feels. I like to fry a few sage leaves in a spoonful of olive oil to add a crispy garnish.
• Kosher salt and pepper are essential to bring out the flavor of all the ingredients.
• No-boil lasagna noodles: These pre-cooked, then dried noodles are very convenient and reduce the labor of making lasagna. As the lasagna bakes, the noodles absorb the moisture released from the other ingredients and the béchamel sauce. Feel free to substitute regular or gluten-free lasagna noodles prepared according to the package instructions and blotted dry.
• Cheeses: Mild mozzarella cheese melts beautifully and helps bind the dish together, while more assertive Parmesan adds wonderful, nutty flavor.

For the Garlic Béchamel Sauce

• Extra virgin olive oil: Butter is the classic base for béchamel, but I found a mild-flavored oil, like our Arbequina from California, is a great alternative that won’t overpower the delicate flavor of this sauce.
  • TRY IT: Premium Extra Virgin Olive Oil from around the world.
• Garlic: A few cloves of chopped garlic infuse the sauce and the entire dish with savory flavor.
• All-purpose flour thickens the béchamel. For a gluten-free alternative, you can use a gluten-free flour blend or a cornstarch slurry.
• Milk is the basis for béchamel sauce. Low-fat, two-percent milk makes for a lighter result, but you can substitute whole milk if you prefer a richer sauce.
• Kosher salt: Salt is key to preventing this sauce from tasting bland.
• Nutmeg: Traditional in béchamel, a touch of grated nutmeg brings a subtle warmth and hint of spice to this mild sauce. Use a rasp grater to grate whole nutmeg for the freshest flavor.

How to Make Butternut Squash Lasagna

The process of making lasagna is complex, but the payoff is worth it! You can make the béchamel in advance and chill it, covered tightly, overnight. When you’re ready to proceed, reheat it gently and whisk it thoroughly to remove any lumps.

• Prep Squash: Trim the stem and bottom ends of a 2 1/2 pound butternut squash, then use a heavy-duty peeler to remove the skin. Halve butternut squash lengthwise and use a spoon to scrape out seeds. Place the squash flat-side down, and cut crosswise into 1/4-inch thick slices. You should have about 8 cups, or 2 pounds. Reserve any remaining squash for another use. 
• Sauté aromatics: Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add 2 cups thinly sliced shallots, and cook, stirring, until golden-brown, about 3 minutes. Stir in 2/3 cup finely chopped walnuts and 1/2 cup thinly sliced sage leaves, and cook until the sage wilts, about 2 minutes more. Season with 1/2 teaspoon salt and a generous amount of freshly ground black pepper.
• Make Béchamel Sauce: Heat 1/4 cup extra virgin olive oil in a saucepan over medium-low heat. Add 4 cloves of minced garlic and cook for 1 minute. Whisk in 4 tablespoons all-purpose flour and cook, stirring, for 3 minutes. Increase the heat to medium and add 4 cups of 2% milk, a few tablespoons at a time, whisking constantly to prevent lumps from forming before adding more. When all the milk has been added, continue cooking, whisking often, until the sauce comes to a simmer, about 20 to 25 minutes. Reduce the heat to low, and continue whisking until the sauce becomes thick enough to coat the back of a spoon.
• Season Béchamel Sauce: Whisk in 1/2 teaspoon salt, a few grinds of freshly ground black pepper, and 1/2 teaspoon finely grated nutmeg. Remove from heat. The béchamel should be thick, but still pourable. Taste and add a pinch more salt if necessary.
• Mix cheeses: In a small bowl, toss 2 cups coarsely grated part-skim mozzarella (8 ounces) and 1 cup finely grated Parmigiano-Reggiano cheese (3 ounces) together.
• Assemble Lasagna: Preheat the oven to 375°F. Brush a 9 x 13-inch baking dish with olive oil. Ladle about 3/4 cup Garlic Béchamel Sauce into the dish and use a rubber spatula to spread it evenly over the bottom. Place 3 no-boil lasagna noodles on top. Ladle another 3/4 cup of béchamel sauce over the noodles and spread it evenly to coat the noodles. Layer on a quarter of the squash slices, slightly overlapping, and sprinkle with salt and ground pepper. Spread a quarter of the shallot-walnut mixture over the squash, and sprinkle with a quarter of the cheese mixture. Make three more layers the same way, beginning with the noodles and ending with the cheese. Add a few more fresh sage leaves on top, if you like.
• Bake Lasagna: Cover the lasagna with foil and place it in the oven. Bake for 1 hour. Remove the foil. Use a sharp paring knife to test for doneness: it should slip easily through the squash and noodles. If squash seems too firm, cover with foil again and return to the oven for up to 15 more minutes.
• Run under the broiler: Remove the foil and turn the oven to broil. Broil until the topping is golden-brown, about 10 minutes (watch carefully to prevent burning). 
• Cool and serve: Let the lasagna cool for 10 minutes before slicing and serving.

Make it Your Own

Adapting a lasagna recipe can be tricky, due to the precise measurements and the fact that the baking temperature and time have been calculated for specific ingredients. I wouldn’t recommend replacing the squash with other vegetables, nor swapping out the béchamel for another type of sauce. However, there are still adjustments you can make to suit your tastes and get delicious results. Here are some ideas:

• Swap the nuts: Finely chopped hazelnuts would be lovely instead of walnuts. Or skip the nuts altogether, if you like a uniformly soft texture. For a nut-free option, use roasted pepitas.
• Swap the herbs: Use fresh thyme instead of sage.
• Change the garnish. I liked the look of the walnuts on top of the finished lasagna, but if you want a cleaner-looking top, split the walnut-shallot mixture among the inner layers instead.
• Use your favorite cheeses: I like the combination of a mild cheese, like mozzarella, with a saltier and more flavorful cheese like Parmesan. But choose your own favorite combo. Unaged fontina and Pecorino-Romano would also be nice. Or, for even more cheesy flavor, try Gruyere and Parmesan.

What to Serve with Butternut Squash Lasagna 

A simple, yet elegant salad like our Butter Lettuce with Tarragon Vinaigrette is the perfect way to balance the rich, creamy lasagna. Or, if you want to stick with the Italian-American theme, try our tangy Caesar Salad with anchovy dressing.

If serving this to company, I’d make a batch of Homemade Garlic Bread, featuring healthy olive oil and lots of fresh herbs, or Homemade Focaccia with Rosemary and Roasted Garlic to go with it. And to end on a sweet note, my vote would be for our easy Italian Pear Cake, flavored with citrus and honey.