Chop the scallion and mozzarella and cut the asparagus into 2-3 cm pieces. Place the chopped scallion in a skillet together with the asparagus and sauté for 5 minutes. Allow to cool and add the mozzarella, ricotta, salt and pepper. Mix well.
Briefly boil the cannelloni (for around 2 minutes) in hot salted water and set aside. Fill a pastry bag with the asparagus mixture and pipe inside each cannelloni. With the remaining chopped scallion and olive oil, prepare the Passata sauce in a small pan for 10 minutes. Arrange the filled cannelloni in a baking pan, cover with the Passata sauce and sprinkle the grated Parmigiano on top.
Bake in the oven for 10 minutes at 180°C. Place on the béchamel sauce when serving.