Trim the woody ends off the asparagus and sliced them into thin rounds.
Sauté the asparagus with thinly sliced leeks (instead of onion) in olive oil for about 10 minutes, until tender.
For the béchamel: mix 2 tbsp flour with a splash of milk and a little olive oil to make a paste.
Heat ~2 cups of milk until almost boiling, then slowly whisk in the paste.
Stir until thick and creamy. Seasoned with salt and nutmeg.
Assemble the lasagna in layers: béchamel, sautéed vegetables, shredded mozzarella, and grated Parmigiano Reggiano. Repeat for all layers.
Bake at 400°F (200°C) for 30 minutes until golden and bubbling.
