Squash and Rapini Lasagna

I've wanted to make this lasagna for months, but was nervous to try it. There are so many steps, and I've never made a bechamel sauce before. It went beautifully-almost. The bechamel didn't thicken up the way it was supposed to, so I ended up adding some corn starch, which did the trick (I've noted below how to do that). The recipe was very labor-intensive, but the final result tasted incredible. The lemon zest added a brightness to the massive amounts of cheese, and the rapini (aka broccoli rabe) cut the sweetness of the butternut squash and, again, the massive amounts of cheese. 

I used this recipe from Bon Appetit with almost no adjustments. One complaint: the recipe called for making the whole box of lasagna, but we ended up using only 12 sheets, which was a bummer to learn after cooking the whole thing. I've noted below how many sheets to use.

Total time to cook: four hours
Makes 10 servings, or more if you cut the pieces smaller

Ingredients:
2 2 lb butternut squash, peeled, deseeded and thinly sliced
4 tbsp olive oil
2 lbs rapini (broccoli rabe), with most of the leaves and stems cut off
1 tsp crushed red pepper flakes
1 lb grated mozzarella cheese
1 lb whole-milk ricotta
2 cups grated parmesean
2 tsp finely chopped fresh sage
Zest of one lemon
1/2 stick margarine (1/4 cup)
1/4/ cup flour
5 cups half and half
1/8 tsp grated nutmeg
1 bay leaf
Lasagna (don't buy the kind that cooks in the oven, and only cook as many sheets as needed for four layers of pasta that cover a 13" by 9" baking dish-for me, 12 thin sheets)
Black pepper and kosher salt, for seasoning

Steps:
Make the squash
- Preheat the oven to 400 degrees. In a large bowl, mix the sliced squash with three tablespoons of olive oil, until the squash is coated. Divide the squash between two baking sheets lined with foil and season with salt and pepper.
- Roast the squash until it's tender, 25 to 30 minutes. Remove the squash and set it aside. You can turn off the oven and preheat again when you're assembling the lasagna.

Make the rapini
- While the squash is roasting, bring salted water (one teaspoon of salt should be fine) to a boil. Blanche the rapini for two minutes. Drain the rapini and squeeze out any water.

- Chop up the rapini and mix it in a bowl with the remaining tablespoon of olive oil, a little salt and pepper, and the red pepper flakes. Set the rapini mixture aside.

Make the cheese mixture 
- In yet another bowl, mix together the mozzarella, ricotta, one cup of grated parmesean, sage, and lemon zest. Cover and keep the cheese mixture in the fridge until you're ready to assemble the lasagna.

Make the bechamel
- In a medium to large pot, melt the margarine over medium to high heat. Mix in the flour, whisking constantly for about two minutes (you don't want the mixture to turn brown).
- Whisk in the half and half, adding one cup at a time and mixing constantly. Add in the nutmeg and bay leaf. Bring the cream to a boil, and then reduce the heat to low and let it simmer for 10 minutes.

- If your cream isn't thickening after 10 minutes (it should have the texture of queso or some other thick cheese sauce), mix three tablespoons of corn starch with a little water in a small bowl, until it resembles a thin paste. Whisk in the corn starch mixture with the cream sauce.
- If your sauce is too thick, add a little more half and half.

Make the lasagna
- In a large pot, bring salted water to a boil. Cook the pasta until its al dente-it shouldn't take more than 10 minutes. Drain the noodles and spread them out on paper towels so they don't stick together.
- In a large, deep baking dish (mine is 13 inches by 9 inches), spread a heaping quarter cup of the bechamel over the bottom of the dish.
- Arrange enough pasta in a single layer to cover the bottom. Add one-third of the squash, one-third of the rapini and one-third of the cheese mixture. Ladle another quarter cup of the bechamel over the squash, rapini and cheese.

- Repeat that layering process two more times, until you've used up the squash, rapini and cheese mixture. Place a final layer of lasagna noodles on top, and then pour the remaining bechamel sauce over the top.
- Sprinkle the second cup of grated parmesean over the top of the lasagna.
- Bake, uncovered, for 45 minutes (the cheese should be starting to brown).
- Finish the lasagna under the broiler for one minute, or as long as it takes for the cheese to brown and get bubbly.
- Let the whole thing rest for at least 20 minutes before serving, which will give the lasagna time to all set together.