Set the lasagna pan on the foil-lined sheet pan.
Determine how many layers you think your lasagna pan will hold (usually, 4-5 layers). Eyeball the ingredients as you go so that you will have enough ingredients for each layer without running out (next time, you will know exactly how many layers your pan holds!)
Coat the bottom of your lasagna pan with sauce, and add a layer of noodles. If they do not fit in your pan perfectly, use the scissors to trim them.
Spread the first layer of noodles with the ricotta mixture, and top with sauce. Sprinkle a layer of mozzarella, followed by a layer of sauce. Now add another layer of noodles, then ricotta, sauce, then mozzarella.
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Continue to build your lasagna in this way, preparing the correct amount of soaked noodles as you go.
Create the top layer as follows: lasagna noodles, then sauce (do not add any more cheese at this point—you will do so later).
Cover the lasagna tightly with foil and bake atop the lined sheet pan for 45 minutes. Remove the foil—the lasagna should be hot throughout, and at least 140–150°F (60–65°C) in the center. If it is not, cover and continue baking in 5-10 minute increments until the correct temperature is reached. Now remove the lasagna from the oven, and discard the foil. Sprinkle a generous layer of mozzarella, and the reserved Parmigiano-Reggiano, evenly across the top.
Return the dish to the oven and bake for another 15-20 minutes, or until bubbly and browned. The center of the lasagna should reach 165°F (74°C); if it has not, you can continue to bake for a bit longer.
If you would like a browner, crispier top, you may turn your oven to broil and crisp the top, watching carefully to ensure that the lasagna does not burn or dry out. You may need to adjust the oven rack to achieve closer proximity to the broiler.
Allow the lasagna to rest for 15 minutes, and serve hot.