Grate the cheese and spread it on a plate lined with parchment paper: now create a disc about 20 cm in diameter and about 2 mm thick. Cook in the microwave for about 2 minutes, or until the Parmesan has melted and formed a golden crust. Cover an upside-down bowl with the wafer (and its baking paper) to shape the basket and leave to cool.
Finely chop the onion and brown it in a pan with extra virgin olive oil, a clove of garlic, and the rosemary sprigs. Remove the rosemary and add the sliced porcini mushrooms, cooking them with a dash of water if necessary. Season with salt and pepper. Now add the dried cranberries and cook for 2 minutes to soften them.
Meanwhile, bring a pot of salted water to a boil and cook the fusilli pasta. Drain the pasta when it is al dente and add it to the sauce.
Toss everything together, adding a ladleful of the pasta cooking water if necessary, to finish cooking and thicken the sauce. Serve the fusilli inside the Parmesan wafer and garnish with a sprig of rosemary.
