• for the spinach:
• 2 Tbsb butter, divided
• 2 Tbsp extra virgin olive oil
• ½ cup shallot, finely minced
• 2 Tbsp garlic, minced
• Kosher salt and freshly ground black pepper
• 2 pounds fresh flat or curly spinach leaves, washed and dried
• for the ricotta:
• 2 pounds fresh ricotta cheese
• 2 large eggs
• 4 ounces finely grated Parmigiano Reggiano cheese
• 1 tsp nutmeg, freshly grated
• for the white sauce:
• 4 Tbsp butter
• ¼ cup flour
• 4 cups (1 quart) whole milk
• 12 ounces grated low moisture mozzarella cheese
• 12 ounces grated Comte, Gruyere, or Emmentaler cheese

for the spinach: Heat olive oil and butter in a large saucepan over medium heat until melted. Add shallots and garlic, season with salt and pepper, and cook, stirring frequently, until softened and fragrant, about 1 minute. Add a few large handfuls of spinach and cook, stirring, until wilted. Continue adding spinach a handful at a time until it is all in the pot.

Cook, stirring frequently, until spinach expels its moisture and most of that moisture evaporates, leaving a dry bottom as you stir. Season to taste with salt and pepper. Transfer spinach to a fine mesh strainer set over the sink and press out excess moisture with a rubber spatula. Let spinach continue to drain as you prepare the ricotta mixture.

for the ricotta: Transfer half of the ricotta, both eggs, the Parmesan, and the nutmeg to the bowl of a food processor. Season with salt and pepper.

Process until completely smooth, about 1 minute.

Transfer the mixture to a large bowl but do not wipe out the food processor. Transfer spinach to food processor and pulse until finely chopped, 10 to 12 short pulses. Add spinach and remaining ricotta to the ricotta mixture and fold gently to combine.

for the white sauce: Heat butter in a medium saucepan over medium heat until melted. Add flour and increase heat to medium-high. Cook, stirring butter and flour with a whisk until pale golden blond, about 1 minute.

Whisking constantly, slowly drizzling in milk. Continue to cook, whisking frequently, until the mixture comes to a boil and thickens. Remove from heat and add ¾ of mozzarella and Comte, Gruyere, or Emmenthale cheese. Whisk until smooth. Season to taste with salt and pepper.

to assemble: Adjust oven rack to lower-middle position and preheat oven to 400°F. Bring a large pot of salted water to a boil. Add pasta sheets a few at a time and cook until barely tender. Transfer to a fine mesh strainer and run under cool water until well chilled. Transfer to a clean kitchen towel in a single layer. Continue until all pasta is par-cooked and dried.

Drizzle a small amount of white sauce over the bottom of a lasagna pan or large casserole. Add a layer of noodles. Top with 1/12th of the spinach mixture and 1/12th of the remaining white sauce. Continue layering pasta, spinach, and white sauce until you lay down the top sheet of pasta. Spread the remaining spinach mixture evenly over the top. Sprinkle with remaining mozzarella and Comte or Emmentaler cheese and drizzle with remaining white sauce. Spread into an even layer with a rubber spatula. Cover tightly with aluminium foil. Bake for 20 minutes. Remove foil and continue baking until bubbly and lightly browned, about 20 minutes longer. Let rest at room temperature for 5 to 10 minutes, then slice and serve.