Add some sliced onion to a pot with warm olive oil. Let it cook for a couple of minutes until soft and golden, then add some finely cut carrot, celery and parsley. Cook and stir for a couple of minutes. In the meantime, you can wash and chop the brown mushrooms.
Add the mushrooms to the pot and let them cook for a couple of minutes. Season with salt and pepper and cook for another couple of minutes while gently stirring.
Add rice to the pot, stir for a minute and add some vegetable broth (or stock). Cook and stir at low/medium heat until the broth reduces, then add some more of it. Repeat the process for 15/20 minutes (depending on the cooking time needed for the kind of rice you use). Always keep an eye on the pot and stir frequently. Also adjust salt and pepper if needed.
Once the risotto is nicely cooked, add some grated truffled pecorino cheese (or a different cheese of your choice). Gently stir for a minute until the cheese is melted.