Step 1

Besciamella: In a medium, heavy-bottomed saucepan over medium-high heat, begin to melt butter. Meanwhile, roughly slice shallot and add to the butter, along with bay leaf, thyme and peppercorns.

Once butter is bubbly, sprinkle in flour and stir constantly until the raw flour is cooked and smells nutty, 4–5 minutes. Reduce heat to medium-low; then slowly add milk while stirring constantly until mixture starts to thicken, 2–3 minutes. Besciamella is done when it coats the back of a spoon. Add nutmeg and season generously with salt to taste.

Place a fine-mesh strainer over a bowl. Remove Besciamella from heat and strain into the bowl; it should be the consistency of thick batter. (Stir in a few tablespoons water if it's too thick.) Cover the surface of the sauce with plastic wrap to prevent a skin from forming until assembly time. Makes 5½–6 cups. (Make ahead and store in the refrigerator for up to 2 days; bring to room temperature before using.)

Step 2

Lasagna sheets: Bring a large pot of water to a boil. Add enough salt to make it taste like the sea. Meanwhile, fill a bowl with ice water and set aside. Line a sheet pan with parchment paper and set aside.

Parcook the lasagna sheets one at a time, in boiling water, for 60 seconds, then transfer to the ice bath for 15 seconds. Place parcooked sheet on the sheet pan and pat dry with a paper towel. Cover with a layer of parchment paper and repeat, creating a stack of sheets, each patted dry and separated by a layer of parchment.

(Note: If using dried lasagna, cook according to manufacturer's instructions.)

Step 3

Pistachio Pesto: In a food processor, add pistachios; pulse a few times to roughly chop. Use a chef's knife to roughly chop arugula, chives, basil, and parsley (a few stems are okay); add to the food processor. (It will seem like a lot of herbs, but just pack them down.) Add Parmigiano, along with a pinch of chile flakes and salt.

Process on high speed, adding lemon juice and oil in a steady stream. (Turn off the motor to scrape down the sides of the bowl as necessary while processing.) Season to taste with salt. Makes 2½–3 cups. (Store in an airtight container in the refrigerator up to 3 days.)

Step 4

Assemble lasagna: Preheat oven to 400 F. In a greased 12 x 7 (2-quart) casserole dish, lay down a lasagna sheet, cutting to fit if necessary; spread 1 cup of Besciamella on top. Add another layer of pasta, then evenly spread ¾ cup Pistachio Pesto on top, followed by ¾ cup mozzarella and ½ cup Parmigiano. Repeat layering 2 more times for a total of 6 pasta layers.

Finish with a final layer of pasta, 1 cup Besciamella, ½ cup Parmigiano, and ½ cup mozzarella. Cover with foil and bake, 25 minutes. Remove foil, then bake another 10 minutes until top is golden brown.

Let cool 15 minutes before plating. Garnish each serving with freshly cracked black pepper and a sprinkle of Parmigiano.