It started when my friend Ann told me about a butternut squash lasagna that she had made - very tasty, but it had no structure. The squash was too loose, basically forming a mush that the noodles floated around in. Definitely not up to lasagna criteria. She was still craving the dish, though, so we went about trying to find a better recipe.
When I eventually stumbled across this recipe on Epicurious, I was intrigued. The hazelnuts, it seemed, would give the filling enough substance to stand up on its own, and I also tend to favor lasagnas that use bechamel, so I was sold. I did have to tweak the recipe anyway, though, because their rendition of bechamel - well, it just didn't work. We had to get out a strainer and there was lost garlic and - yeah, not worth it. I've subbed in a better (and easier) version of bechamel below.
We served with with some pan-fried kielbasa, and I think it was almost needed. The saltiness of the meat cut the sweetness of the lasagna and made for a more balanced flavor.
Also, my cheese measurements are approximate. I'm not one to cook with definite quantities (especially of things like cheese), so really, feel free to put in as much or as little cheese as you see fit (although, if you see fit to add less, we can no longer be friends).
For the filling:
1 large onion, chopped
3 Tbsp butter
3 lb butternut squash, peeled, seeded, and cut into 1/4 inch cubes
1 tsp minced garlic
1 tsp salt
1/4 tsp white pepper
2 Tbsp parsley, chopped
1 Tbsp fresh sage, chopped
1 cup hazelnuts, toasted, loose skins removed, and finely chopped
For the bechamel:
5 Tbsp butter
4 Tbsp flour
5 cups milk
1 bay leaf
1 tsp minced garlic
1/2 tsp freshly grated nutmeg
2 tsp salt
2 cups coarsely grated mozzarella
1 cup finely grated pecorino Romano
1 lb fresh lasagna noodles, uncooked (you can use 12 sheets of no-boil lasagna noodles if you can't make or buy fresh pasta)
In a large skillet, melt butter over medium heat. Add onion and cook until golden, about 10 minutes. Add squash, garlic, salt, and white pepper, and continue to cook until the squash is tender, 10-15 minutes. Remove from heat and stir in parsley, sage, and half of the hazelnuts. Let cool slightly, then puree in a blender until smooth (if you like it a little chunkier, puree with an immersion blender). Set aside.
For the bechamel, using a small sauce pot on medium-low, heat butter until melted. Add flour and stir until smooth. Over medium heat, cook until the mixture is golden, stiring constantly, about 6 minutes. In a separate pot, heat milk until almost boiling. Add milk to butter, 1 cup at a time, whisking until smooth. Bring to a boil, add bay leaf and garlic, and cook for 10 minutes, stirring constantly. Remove from heat and add salt and nutmeg; remove bay leaf.
To assemble the lasagna, spread about 1/2 cup of the sauce on the bottom of a 13x9 glass baking dish. Lay down pasta sheets to cover the bottom of the pan, making sure they do not overlap. Spread with 2/3 cup of the sauce, then a third of the squash filling, then a half cup of mozzarella. Sprinkle with pecorino and remaining hazelnuts. Repeat layering process two more times, going from pasta to cheese and nuts. Finish with a layer of pasta topped with the remaining bechamel and cheese.
To bake, preheat oven to 425°. Cover the baking dish tightly with foil and bake in the middle of the oven for 30 minutes. Remove foil and bake for another 15 minutes, until the top is golden and bubbly. Let lasagna sit for 15 minutes before serving.