Heat stock in a saucepan and keep it on a low simmer.
Place the porcini mushrooms in a bowl and pour in just enough hot stock to cover. Leave for a couple of minutes until they've softened. Fish them out of the stock and chop them, reserving the soaking liquid.
In a large pan, heat a glug of olive oil and add the onion and celery. Slowly fry without coloring for at least 10 minutes, then turn the heat up and add the rice. Give it a stir. Stir in the vermouth or wine - it'll smell fantastic! Keep stirring until the liquid has cooked into the rice. Now pour the porcini soaking liquid through a sieve into the pan and add the chopped porcini, a good pinch of salt and your first ladle of hot stock. Turn the heat down to a simmer and keep adding ladlefuls of stock, stirring and massaging the starch out of the rice, allowing each ladleful to be absorbed before adding the next. Carry on adding stock until the rice is soft but with a slight bite. This will take about 30 minutes.
Meanwhile, get a dry griddle pan hot and grill the wild mushrooms until soft. If your pan isn't big enough, do this in batches. Put them into a bowl and add the chopped herbs, a pinch of salt and the lemon juice. Using your hands toss everything together - this is going to be incredible!
Take the risotto off the heat and check the seasoning carefully. Stir in the butter and the Parmesan. You want it to be creamy and oozy in texture, so add a bit more stock if you think it needs it. Put a lid on and leave the risotto to relax for about 3 minutes.
Taste your risotto and add a little more seasoning or Parmesan if you like. Serve a good dollop of risotto topped with some grilled dressed mushrooms, a sprinkling of freshly grated Parmesan and a drizzle of extra-virgin olive oil.
Recipe Excerpted from JAMIE AT HOME by Jamie Oliver. Copyright (c) 2008. Published in the U.S. by Hyperion. All Rights Reserved. www.jamieoliver.com