Ingredients

For Squash Filling:

• 3 pounds butternut squash, peeled, seeded, and cut into 1/2-inch pieces
• 1 large onion, thinly sliced
• 3 tbsp unsalted butter
• 1 tsp minced garlic
• 1 tsp salt
• 1/4 tsp white pepper
• 2 tbsp chopped fresh flat-leaf parsley
• 4 tsp chopped fresh sage
• 1 cup hazelnuts (4 ounces), toasted, loose skins rubbed off with a kitchen towel, and coarsely chopped

For Sauce:

• 1 tsp minced garlic
• 3 tbsp unsalted butter
• 5 tbsp all-purpose flour
• 5 cups milk
• 1 bay leaf
• 1 tsp salt
• 1/2 tsp freshly grated nutmeg
• 1/8 tsp white pepper

For Assembling Lasagne:

• 1/2 pound fresh mozzarella, coarsely grated (2 cups)
• 1 cup finely grated Parmigiano-Reggiano (3 oz)
• 12 (7- by 3 1/2-inch) sheets no-boil lasagne (1/2 lb)

Instructions

Make Filling:

Spread butternut squash over two sheet pans, in even layers. Roast the butternut squash on at 350°F until tender, about 30 minutes. Meanwhile, cook onion in butter in a deep 12-inch heavy skillet over moderate heat, stirring occasionally, until golden, about 10 minutes. Add squash, garlic, salt, and white pepper and cook, stirring occasionally, until heated through, about 5 minutes. Remove from heat and stir in parsley and sage. Cool filling.

Make Sauce:

Cook garlic in butter in a 3-quart heavy saucepan over moderately low heat, stirring, 1 minute. Whisk in flour and cook roux, whisking, 3 minutes. Add milk in a stream, whisking. Add bay leaf and bring to a boil, whisking constantly, then reduce heat and simmer, whisking occasionally, 10 minutes. Whisk in salt, nutmeg and white pepper and remove from heat. Discard bay leaf. (Cover surface of sauce with wax paper if not using immediately.)

Assemble Lasagne:

Preheat oven to 425°F. Toss cheeses together.

Spread 1/2 cup sauce in a buttered 13- x 9- x 2-inch glass baking dish (or other shallow 3-quart baking dish) and cover with 3 pasta sheets, leaving spaces between sheets. Spread with 2/3 cup sauce and one third of filling, then sprinkle with a heaping 1/2 cup cheese and 1/3 of the nuts. Repeat layering 2 more times, beginning with pasta sheets and ending with nuts. Top with remaining 3 pasta sheets, remaining sauce, remaining cheese and nuts.

Tightly cover baking dish with buttered foil and bake lasagne in middle of oven 30 minutes. Remove foil and bake until golden and bubbling, 10 to 15 minutes more. Let lasagne stand 15 to 20 minutes before serving.

Chef’s Note:

Filling and sauce can be made 1 day ahead and kept separately, covered and chilled. Bring to room temperature before assembling.

If you want to make the lasagna further in advance, you can prepare it all of the way through the assembly and then freeze it unbaked. When you are ready to bake it, just double the time for a total of 90 minutes of bake time. There is no need to defrost the lasagna.

Be careful that the baking dish that you’ve frozen the lasagna in can go from freezer to oven. Mine didn’t so I lined the dish with foil, layered the lasagna, covered it in the foil and placed it all in the freezer. Once frozen, I removed the foil lasagna packet from the dish and kept the packet in the freezer. When I was ready to bake it, I removed the foil and popped the lasagna back into the original baking dish.

Recipe adapted from Epicurious