Cook the pasta in a large saucepan of salted boiling water until it is al dente: according to the packet instructions for dried pasta or for 2–3 minutes if using fresh pasta.
Meanwhile, heat the oil in a saucepan over a medium heat, add the garlic and porcini and cook, stirring frequently, for 4 minutes. Cut the prosciutto into strips, trying to keep them separate. Add to the porcini mixture with the cream and parsley and season with salt and pepper. Bring to the boil, then reduce the heat and simmer for 1 minute.
Drain the pasta, add to the sauce and toss well, using 2 spoons to mix evenly. Scatter with the Parmesan, toss well and serve immediately.