Squash and Broccoli Rabe Lasagna

Ingredients

• 2 2-lb. butternut squash, peeled, halved, seeded, cut crosswise into 1/4-inch-thick slices
• 3 tablespoons olive oil plus more t
• Kosher salt, freshly ground pepper
• 2 pounds broccoli rabe (rapini), tough stems removed
• Crushed red pepper flakes
• 1 pound fresh mozzarella, coarsely grated
• 1 pound whole-milk ricotta
• 1 cup finely grated Parmesan
• 1 tablespoon finely grated lemon zest
• 2 teaspoons minced fresh sage
• 1 teaspoon minced fresh rosemary
• 1/4 cup (1/2 stick) unsalted butter
• 1/4 cup unbleached all-purpose flour
• 5 cups (or more) half-and-half
• 1/8 teaspoon (or more) freshly grated nutmeg
• 1 bay leaf
• Kosher salt, freshly ground pepper
• 1 pound lasagna noodles
• 3/4 cup finely grated Parmesan

Directions

• 1.

  Preheat oven to 400°. Place squash and 3 tablespoons oil in a large bowl; season generously with salt and pepper and toss to evenly coat squash. Transfer to 2 rimmed baking sheets, spreading out in a single layer, overlapping slightly. Roast until tender but not mushy, about 15 minutes. Let cool.

• 2.

  Quickly blanch broccoli rabe in a large pot of boiling salted water just until it wilts, 1–2 minutes. Drain; briefly cool under running water. Squeeze out excess water; coarsely chop and transfer to a large bowl. Season with salt, pepper, and red pepper flakes; drizzle with oil and toss to coat.

• 3.

  Mix mozzarella and next 5 ingredients in a large bowl; season with salt and pepper. DO AHEAD Squash, broccoli rabe, and cheese mixture can be made 1 day ahead. Cover separately and chill.

• 4.

  Melt butter in a large heavy saucepan over medium heat. Add flour; stir until slightly thickened (do not allow mixture to turn brown), 2–3 minutes. Increase heat slightly; slowly whisk in 5 cups half-and-half, 1/2-cupful at a time, allowing béchamel to thicken between additions (adding half-and-half gradually will help to prevent lumps from forming). Add 1/8 teaspoon nutmeg and bay leaf.

• 5.

  Reduce heat to low and cook, thinning with more half-and-half if too thick, until sauce is a milk shake–like consistency, about 10 minutes longer. Season to taste with salt and pepper. Strain through a fine-mesh sieve into a medium metal bowl. Set bowl over a large saucepan of gently simmering water. Cover and keep warm.

• 6.

  Cook lasagna noodles in a pot of well-salted boiling water until still quite al dente, 8–9 minutes. Transfer immediately to a large bowl of ice water to cool. Drain; spread out noodles on a kitchen towel or baking sheets lined with parchment paper, placing a kitchen towel or parchment between layers.

• 7.

  Ladle about 1/4 cup béchamel into a 13x9x2-inch baking dish; spread evenly over bottom. Line dish with a single layer of noodles, cutting as needed to fit (use large scraps in subsequent layers). Layer 1/3 of squash over. Scatter 1/3 of broccoli rabe over. Dollop 1/3 of ricotta mixture randomly over greens. Drizzle 1/2 cup béchamel evenly over ricotta mixture. Repeat process 2 more times for a Total of 3 layers, finishing with a layer of noodles. Spread remaining béchamel over; top with Parmesan. DO AHEAD Lasagna can be assembled 1 day ahead. Cover and chill. Return to room temperature before continuing.

• 8.

  Preheat oven to 375°. Bake lasagna uncovered until bubbly and starting to brown, about 45 minutes. Turn oven to broil. Cook until browned and golden, 4–7 minutes. Let rest for 20–30 minutes before serving.