Adapted from The Big Lasagna recipe by the New York Times
Ingredients
Ricotta Filling
4 Tbsp EVOO
1 pound fresh mature spinach, washed and ends trimmed, or 1½ cups frozen spinach, thawed
Fine sea salt
2 pounds whole-milk or part-skim ricotta (about 4 cups)
6 oz grated whole-milk or part-skim mozzarella (2 cups)
3 oz freshly grated parmesan (1 heaping cup)
20 large fresh basil leaves, finely chopped (about ¾ cup)
2 Tbsp fresh Italian parsley, finely chopped
1 tsp fresh thyme, finely chopped
1 tsp dried Italian seasoning
Béchamel
½ cup unsalted butter (1 stick)
½ cup all-purpose flour
4 cups whole milk
Fine sea salt
Freshly ground black pepper
Ground nutmeg
Assembled Lasagna
4½ cups tomato sauce (see Simple Marinara in “Sauces” folder)
Fine sea salt
2 (9 oz) packages dried lasagna noodles
1½ oz grated parmesan
3 oz grated whole-milk or part-skim mozzarella
Directions
Prepare the ricotta filling: If using fresh spinach, set a large skillet over high heat. (If using thawed frozen spinach, skip to Step 2.) When hot, add 2 tablespoons oil and half the fresh spinach. Season with a pinch of salt and sauté to wilt. Cook until stems are tender, about 3 minutes. Transfer to a baking sheet and allow to cool in a single layer. Repeat with remaining spinach.
While spinach cools, combine ricotta, mozzarella, Parmesan, basil, and a generous pinch of salt in a large bowl.
Taking handfuls of the cooled or thawed spinach, squeeze out as much water as possible, then chop finely and add to cheese mixture. Mix thoroughly, then taste and adjust seasoning for salt. (Filling makes about 6 cups.) Cover and set aside until ready to assemble lasagna. (Ricotta filling can be made 1 day in advance and refrigerated. Bring to room temperature before assembling lasagna.)
Prepare the béchamel: Set a large, heavy-bottomed pot or Dutch oven over medium heat and add butter. Once butter has melted, whisk in flour, reduce heat to very low and cook for about 15 minutes, stirring regularly to prevent browning. After the mixture foams a bit, it will visibly transform—the butter will separate, the bubbles will reduce in size, and the mixture will look like freshly wet fine sand. Whisking vigorously, slowly pour in milk. Increase heat to medium and whisk until the mixture thickens, about 2 minutes. Add salt, pepper, and nutmeg to taste.
Return heat to low. Continue cooking, whisking regularly for 10 to 15 minutes until the sauce is thick and smooth, with no raw flour flavor. Taste and adjust seasoning with salt. If béchamel is lumpy, strain through a fine sieve or purée with an immersion blender. (You’ll have about 3½ cups.) Press a piece of parchment or plastic against the surface of the sauce to prevent a skin from forming and set aside until ready to assemble lasagna. (Béchamel can be made up to 1 day in advance, covered directly and refrigerated. Return to room temperature before using.)
Prepare the lasagna: Position the highest rack in the oven so that it sits about 6 inches below the top. Heat oven to 400°F.
If tomato sauce, béchamel, and ricotta filling are cold, bring to room temperature or warm them as needed.
Spoon about ¾ cup béchamel into a 9-by-13-inch metal, glass, or ceramic baking pan, and use a rubber spatula or your hands to generously coat bottom and sides of pan with sauce.
Use 2 or 3 sheets of pasta to entirely cover the bottom of the pan, with minimal overlap.
Crumble about ⅓ of the ricotta mixture evenly over pasta to create foundation, then layer with sheets of pasta from edge to edge of pan. (If using store-bought or dried pasta, you can skip the noodle layer between the ricotta and tomato sauce as needed to prevent lasagna from stretching higher than the top of the pan.)
Spread about ⅓ of the tomato sauce over next layer and cover with pasta.
Spread about 1 cup béchamel evenly over next layer, sprinkle with ¼ cup grated Parmesan, and cover with pasta.
Repeat with remaining layers: ricotta, tomato sauce, béchamel and Parmesan, ricotta, tomato sauce, béchamel and Parmesan, following each with a layer of pasta. (If using thicker noodles, you might not be able to fit 8 layers of noodles in the pan.)
For the top, spread with remaining béchamel over a pasta layer. Gently cover lasagna with piece of parchment and wrap tightly with foil. Place onto a baking sheet to catch any overflow and bake on prepared rack.
After 40 minutes, pull lasagna from oven and carefully remove foil and parchment. Sprinkle with grated mozzarella and return to oven until golden brown and bubbling on surface, about 20 minutes.
Allow to cool for at least 15 minutes before slicing and serving. Leftover lasagna can be wrapped and refrigerated for up to 4 days. To freeze, bake 30 minutes but do not brown, then cool, and freeze for up to 4 weeks. Defrost, then sprinkle with mozzarella and bake uncovered at 400°F for 25-30 minutes until golden brown and bubbling on surface.