In a heavy based saucepan with a round bottom, fry the onion in half the butter and the olive oil. When the onion turns colour add the white mushrooms and fry for a few minutes. Add the chopped porcini mushrooms and continue frying, then add the sliced ones.

Add the rice and ensure the butter and mushroom mix has coated the rice and starts sticking. Add the mixed herbs, then start adding the stock, one ladleful at a time. Continue to stir and add the stock until the rice appears to be cooked.

It should be al dente after approximately 20 minutes. Remove the risotto from the heat and, without stirring, add the remaining butter, the grated Parmesan and 3 drops of truffle oil, if using. Season to taste. Add the parsley, give one last stir and serve immediately.