Step 1

MAKE THE PIE: Heat the oven to 400 degrees. Grease a 9-inch springform cake pan then line it with a piece of parchment paper large enough to cover the base and hang over the sides by a couple inches; set aside.

Step 2

MAKE THE RED PEPPER SAUCE: Add the oil to a small frying pan and heat over medium-high. Once it’s hot, add the garlic and cook for about 1 minute, stirring until fragrant but not browned. Add the tomato paste, cumin, coriander and chile flakes and cook for 1 minute more, stirring often, until deeply red. Set aside to cool slightly, then add to a small food processor with the red peppers, sugar, ½ teaspoon salt and a good grind of pepper; blitz until smooth.

Step 3

MIX TOGETHER THE LASAGNA INGREDIENTS AND BAKE: Empty the mixture into a very large bowl and add the squash, lasagna sheets, spinach, basil, feta, Parmesan, 1¼ teaspoons salt and a good grind of pepper. Use your hands to make sure everything is nicely coated. Transfer this mixture to your lined cake pan, adding a third at a time and pressing lightly to ensure everything is even and compact. Using heavy-duty aluminum foil, wrap the cake pan all around until tightly sealed, place on a baking sheet and bake for 1 hour.

Step 4

MAKE THE BÉCHAMEL: Toward the last 15 minutes of baking time, make the béchamel: Melt the butter in a medium saucepan over medium-high heat. Whisk in the flour and cook, whisking steadily, for 2 to 3 minutes, or until it starts to smell like popcorn. Slowly pour in the milk ½ cup at a time, whisking with each addition until fully incorporated. Turn the heat down to medium. Then add the garlic and ¼ teaspoon salt. Use a spatula to stir and cook for 2 minutes, stirring to ensure the bottom doesn’t scorch, until nice and smooth. Off the heat, stir in the Parmesan. If the pie isn’t done, cover the top with a piece of parchment paper to prevent a skin from forming. The béchamel is easier to handle when warm; if needed, reheat gently with a splash of milk to loosen.

Step 5

SPOON THE BÉCHAMEL ON TOP: After the pie has cooked for 1 hour, remove it from the oven and carefully unwrap the top foil and paper, crinkling it down and around the sides of the pan to expose the top. Spoon the béchamel on top, using a spatula to distribute it evenly over the surface. (Take care not to mix it with the base; you want the béchamel to remain white.)

Step 6

FINISH THE BAKE AT 450°F: Turn the oven temperature up to 450 degrees, place the cake pan back on its baking sheet and bake for another 15 to 20 minutes, rotating halfway through, until nicely browned on top. Set aside to cool for at least 15 minutes.

Step 7

SERVE: Carefully release the pie from the springform pan, loosening the outer ring then using the parchment to help lift it onto a serving plate or board. Serve warm or at room temperature.