Prepare the ricotta filling: Mix ricotta, lemon zest, grated Parmesan, chopped basil, salt, pepper, and olive oil.
Prepare the asparagus béchamel: Use the asparagus trimmings. Boil the milk with the asparagus trimmings, blend and sieve. Make a béchamel sauce with milk, butter, flour, asparagus trimmings, salt, pepper, and nutmeg.
Blanche the asparagus spears and refresh in iced water.
Assemble the cannelloni: pipe a line of ricotta mix on the lasagna sheets and then place a spear of asparagus on each one, roll up.
Place a thin layer asparagus bechamel on the bottom of a baking dish. Place the cannelloni, cover with the rest of the bechamel.
Top with grated Parmesan.
Bake until golden brown and bubbly - 15 mins @ 220c.
