Cheesy Spinach Lasagna

Directions

1. For the Pasta
2. If using fresh pasta sheets, make the dough: Make the pasta dough by hand according to the "well method" (see Author Notes). Alternatively, add the flour and eggs to the bowl of a stand mixer fitted with the dough hook. Mix on low speed, scraping down the sides of the bowl as needed, until the mixture comes together, about 7 minutes. Transfer the dough to a flat, ideally wooden work surface and knead for 2 to 3 minutes, until smooth and firm.
3. Wrap the dough tightly in plastic and allow it to rest at room temperature for 30 minutes to 1 hour. In the meantime, prepare the fillings. If using dry pasta, no need to do any additional preparation.

1. For the Lasagna Filling & Assembly
2. Make the spinach mixture: Wash and roughly chop the greens (if using chard or kale, remove the ribs and reserve for another use). Line a sheet pan with a clean dish cloth and keep it nearby.
   
   In a Dutch oven or large pot with a lid, warm the butter or olive oil over medium heat. Add the onion or shallot, garlic, and a pinch of salt and pepper. Cook, stirring occasionally, until softened and fragrant, 5 to 7 minutes.
   
   Reduce the heat to medium-low. Add half of the greens and stir to combine with the onion and garlic. Add a splash of water, cover, and cook until the greens are beginning to wilt, 2 minutes. Uncover the pot and stir until wilted, then press them down and add the rest of the greens, along with a generous pinch of salt and pepper. Stir to combine as best you can. Pour in another splash of water and cover the pot. Cook, uncovering occasionally to stir, until mostly wilted, 5 to 7 minutes. Uncover and stir until completely wilted.
   
   Drain the greens in a colander, pressing out as much moisture as possible, and allow to cool. Then transfer them to the dish cloth and wring out as much of the remaining water as you can.
   
   Combine the greens, ricotta, mascarpone, and Parmigiano Reggiano in a food processor fitted with the steel blade. Season generously with salt, pepper, and freshly grated nutmeg to taste. Pulse until very finely chopped but not puréed and adjust the seasoning as needed. Transfer the mixture to a large bowl. Fold in the egg and another pinch of salt and mix until incorporated. Set aside.
3. Make the cheese sauce: In a medium saucepan, melt the butter over medium heat. Add the flour and cook, using a whisk to mix constantly, until it smells nutty and the mixture starts to loosen and bubble, 2 minutes.
   
   While whisking constantly, gradually add the milk, either in a slow, steady stream or a splash at a time.
   
   Increase the heat to medium-high and cook, still whisking, until the milk starts to bubble and thicken. When it coats the back of a spoon (about 7 minutes), turn off the heat. Whisk in the Fontina and mozzarella, one handful at a time, until smooth. Season to taste with salt and pepper and set aside. Cover the sauce or whisk from time to time to prevent a skin from forming on the surface.
4. Roll out and boil the pasta: Heat the oven to 375°F. Bring a large pot of water to a boil and salt it generously.
   
   If using store-bought dried lasagna sheets, cook according to the package directions. If making fresh pasta sheets, cut off one-sixth of the dough (about 130 grams/4.5 ounces) and rewrap the rest immediately. Flatten the dough with the heel of your hand until it’s about ¼ inch thick.
   
   Set your pasta machine to its widest setting and roll the dough through once (it will be tapered at the ends). Rotate the dough 90 degrees and fold both ends into the center like an envelope, so the width of the pasta sheet is similar in width to the pasta roller (about 6 inches). Roll the dough through the widest setting once more—aligning the widths—so the result is a mostly even rectangle.
   
   Continue rolling the pasta through the machine once on each progressive setting until you have a thin sheet (setting 7 on a Marcato Atlas 150 manual roller, or setting 6 twice through the KitchenAid attachment). If the dough is at all sticky as it goes through the machine, dust both sides with a little ‘00’ or all-purpose flour.
   
   Trim any uneven ends from the pasta sheet—ball them up and wrap them in plastic wrap—then cut it into approximately 11-inch-long rectangles (you should be able to get 2 pieces). Add any additional scraps to the ball in the plastic wrap: Once you’ve used all the fresh dough, you can reroll the accumulated scrap ball through the machine a second time. (Any leftovers can be made into fettuccine or whatever you want!)
   
   Line a sheet pan with a clean dish cloth. Fill a large bowl with ice water. Place the pasta sheets in the boiling water and gently stir. Cook for about 30 seconds, then use a spider and/or tongs to carefully transfer to the ice bath (alternatively, you can rinse the pasta under cold water in a colander). Place the pasta on the dish cloth and pat dry, then cut one of the pieces in half lengthwise, so you have 2 long strips. (You’ll need 9 pasta sheets total: 6 will stay as they are and 3 will be cut in half lengthwise.)
5. Assemble the lasagna: Ladle a thin layer of the cheese sauce into a 9x13-inch (or another 3-quart) baking dish, spreading it out with the bottom of the ladle or a spoon. Layer one wide pasta sheet and one of the thinner strips on top to fill the dish, overlapping as needed. Spoon over a layer of the spinach mixture (about one-sixth if using fresh pasta and about one-quarter if using dry pasta) and spread it across the pasta using the back of the spoon or an offset spatula—don’t worry if there are some gaps. Then add another thin layer of cheese sauce and spread it out over the spinach.
   
   Roll out another section of pasta dough and blanch the sheets in the water. Shock in the ice bath (or rinse) and pat dry on the dish cloth, then add them to the baking dish, followed by another layer of the spinach mixture and layer cheese sauce. Repeat the process until you have 6 layers (if using fresh pasta; 4 to 5 layers if using dry), ending with cheese sauce. Cut some of the cooked pasta sheets in half (whether using fresh or dry pasta) and roll out and cook the scrap ball as needed (if using fresh pasta). Sprinkle with a generous amount of grated Fontina, mozzarella, and lots of Parmigiano Reggiano.
6. Bake the lasagna: Cover the baking dish tightly with foil and bake for 30 minutes. Uncover and bake until bubbling and golden around the edges, 15 to 20 minutes more. Broil the top for a few minutes for extra color, then remove from the oven. Let stand for at least 10 minutes (or up to 2 hours at room temperature) before serving.