In a saucepan, gently sauté the finely chopped white onion together with the fresh sausage, removed from its casing. Break the sausage into small pieces as it cooks, allowing it to release some of its fat. Add the wild fennel seeds and tomato passata, then simmer over medium heat for approximately 25 minutes.
Only once the ragù is fully cooked, stir in the saffron powder and adjust the seasoning with salt if necessary.
Bring a large pot of salted water to the boil and cook the conchiglioni until al dente. Drain, toss with extra virgin olive oil and set aside.
Meanwhile, place the RICOTTA in a bowl and season with a pinch of salt and the saffron powder. Add a little pasta cooking water to obtain a smooth, creamy filling.
Fill the conchiglioni with the RICOTTA mixture, allowing approximately 5 pasta shells per person. Arrange them in an ovenproof dish and bake for a few minutes at 150°C (300°F).
Using a knife, shave the ROCCA RUYA into thin flakes and set aside for the final presentation.
Arrange the filled conchiglioni on the plates and spoon the sausage ragù over them. Just before serving, finish with the ROCCA RUYA flakes.