Butternut Squash Lasagna with Swiss Chard

Ingredients

For squash filling

• 1 large onion, chopped
• 3 tablespoons unsalted butter
• 3 lb butternut squash, peeled, seeded, and cut into 1/2-inch pieces
• 1 teaspoon minced garlic
• 1 teaspoon salt
• 1/4 teaspoon white pepper
• 2 tablespoons chopped fresh flat-leaf parsley
• 4 teaspoons chopped fresh sage
• 1 cup walnuts, loose skins rubbed off with a kitchen towel, and coarsely chopped

• 1 teaspoon minced garlic
• 3 tablespoons unsalted butter
• 5 tablespoons all-purpose flour
• 5 cups milk
• 1 bay leaf (not California)
• 1 teaspoon salt
• 1/8 teaspoon white pepper

• 1 c whole milk ricotta cheese
• 2 eggs, whisked
• 1 lb swiss chard, stems removed, chopped and sauteed, drained and pureed
• 1/2 lb fresh mozzarella, coarsely grated (2 cups)
• 1 cup finely grated Parmigiano-Reggiano (3 oz)
• 12 (7- by 3 1/2-inch) sheets par boiled lasagna noodles (1/2 lb)

Preparation

Make filling:

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 squash is just tender, about 15 minutes. Remove from heat and stir in parsley, sage, and nuts. Cool filling.

Make sauce while squash cooks:

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 and white pepper and remove from heat. Discard bay leaf. (Cover surface of sauce with wax paper if not using immediately.)

Assemble lasagna:

Preheat oven to 425°F. Combine ricotta and eggs with pureed swiss chard. Toss cheeses together and mix half into ricotta. Spread 1/2 cup sauce in a buttered 13- by 9- by 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 heaping 1/2 cup ricotta cheese mixture. Repeat layering 2 more times, beginning with pasta sheets and ending with cheese. Top with remaining 3 pasta sheets, remaining sauce, and remaining mozzarella and parmesan cheese.

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