Heat the oil in a non-stick frying pan. Stir fry the asparagus pieces for approx. 8 mins., season, puree, leave to cool.
Add the ricotta and parmesan, mix well.
Cut the pasta dough in half crosswise, then cut lengthwise into four equal pieces. Spoon approx. 2 1/2 tbsp of filling onto each piece of pasta, place approx. 2 of the reserved asparagus tips in the middle of each, roll up. Transfer to the prepared baking dish, reserving approx. 4 tbsp of filling.
Combine the cream, cheese and reserved filling, season, pour over the cannelloni.
Approx. 20 mins. in the centre of an oven preheated to 220°C, remove.
Sprinkle with lemon balm.