Butternut squash-sweet potato moussaka recipe

Ingredients

• 4 tablespoons (½ stick / 55 g) unsalted butter
• ¼ cup (30 g) all-purpose flour
• 1 quart (1 L) whole milk, at room temperature
• 2 large eggs, lightly beaten
• 1 cup (150 g) grated or crumbled Greek feta
• ½ cup (50 g) Kefalotyri or pecorino cheese
• ½ teaspoon freshly grated nutmeg
• Salt and freshly ground black pepper

• 1 tablespoon butter
• 1 cup (240 ml) extra-virgin Greek olive oil
• 4 large red onions, coarsely chopped
• 3 pounds (1.4 kg) butternut or calabaza squash, peeled, seeded, and cut into ¼-inch-thick (6 mm) slices
• Salt
• 1½ pounds (680 g) sweet potatoes or yams, peeled and cut lengthwise into ¼-inch-thick (6 mm) slices

• Olive oil
• Salt and freshly ground black pepper
• 1 cup (50 g) chopped fresh mint
• ½ cup (25 g) chopped fresh parsley

Make the Bechamel
1. In a large pot, melt the butter over medium heat. When it has completely melted and stopped bubbling, but before it turns brown, add the flour and whisk to incorporate. Cook, whisking, until the mixture is lightly colored, about 5 minutes. While whisking, slowly pour in the milk and continue whisking until the sauce thickens, 10 to 12 minutes total. Remove from the heat. While whisking vigorously, pour in the eggs and whisk until incorporated. Stir in the cheeses. Season with the nutmeg and salt and pepper to taste. Set aside, covered with a kitchen towel.
Cook the Vegetables
2. In a large wide pot or deep skillet, heat the butter and 1 tablespoon of the olive oil together over medium heat until the mixture begins to bubble softly. Add the onions, reduce the heat to low, and cook for about 20 minutes, until the onions are lightly golden.
3. Preheat the oven to 350ºF (175ºC). Line two baking sheets with parchment paper.
4. In a large basin or bowl, toss the squash with ½ cup (120 ml) of the olive oil. Spread the pieces in one layer on the baking sheets and sprinkle lightly with a little salt. Bake for 10 to 12 minutes, turning once, until softened but not thoroughly cooked. Remove from the oven and transfer the squash to a large plate; set aside. Keep the oven on.
To Assemble the Moussaka
5. Lightly oil a large baking pan. Layer the sweet potatoes in the bottom of the pan. Season with salt and pepper and sprinkle with ⅓ cup (17 g) of the mint. Sprinkle with a little of the parsley. Spread a scant layer of the caramelized onions on top. Pour about one-third of the béchamel over the onions, spreading it out evenly with a spatula. Repeat with a layer of butternut squash, salt and pepper, mint, parsley, onions, and a little béchamel. Repeat once more with more squash, topping that, too, with salt and pepper, mint, parsley, onions, and a final coating of béchamel. Bake for 35 to 40 minutes, until the béchamel is puffed and golden and the vegetables are tender. Remove from the oven and let rest for 15 to 20 minutes before serving.