Preheat oven to 180°C. Bring a large pot of salted water to boil and cook lasagna sheets according to package instructions until al dente. Drain and lay flat on oiled baking sheets to prevent sticking.

Blend pistachios in a food processor until finely ground, reserving 2 tablespoons for garnish. Set aside.

Make the pistachio béchamel: Melt butter in a medium saucepan over medium heat. Add flour and whisk continuously for 2 minutes. Gradually pour in milk while whisking to prevent lumps. Stir in ground pistachios and nutmeg. Simmer for 8-10 minutes until sauce thickens and coats the back of a spoon. Season with salt and pepper.

Heat olive oil in a large frying pan over medium heat. Sauté shallot and garlic for 2 minutes until softened. Add asparagus pieces and cook for 4-5 minutes until bright green and just tender. Add spinach and cook until wilted, about 2 minutes. Remove from heat and stir in lemon zest.

In a small bowl, mix ricotta with a pinch of salt and pepper.

Spread a thin layer of pistachio béchamel on the bottom of a 23x33cm baking dish. Layer 4 lasagna sheets, followed by one-third of the remaining béchamel, half the vegetable mixture, and dollops of half the ricotta.

Repeat layers: 4 lasagna sheets, one-third béchamel, remaining vegetables, and remaining ricotta. Top with final 4 lasagna sheets and remaining béchamel.

Sprinkle mozzarella and Parmesan evenly over the top. Cover with foil and bake for 25 minutes. Remove foil and bake for an additional 15-20 minutes until golden and bubbling.

Allow lasagna to rest for 10 minutes before serving. Garnish with reserved crushed pistachios and fresh basil leaves.