You can either use fresh mushrooms or dried porcini mushrooms (which give it a better flavour) If using dried mushrooms, soak them first in hot water. First fry some onion and garlic in a mixture of butter and olive oil. Add the fresh mushrooms. Cook for 2-3 mins until the onions are translucent. Add Arborio or Carnaroli rice and stir well until every grain is well coated. Cook for a minute or so but don't let the rice burn. Add a splash of white wine and stir well. Once the liquid disappears, continue adding ladle after ladle of hot stock. After each ladle, stir well until it the liquid has been absorbed. This should take about 18 minutes until the rice is cooked.. At this point add the soaked mushrooms if you are using them. Add loads of grated parmesan and stir through before serving. You can add parmsan shavings to serve.