Dried porcini, not fresh, and don't let anyone tell you this is a compromise -- drying concentrates a mushroom's flavor rather than diminishing it, and the soaking water becomes half the stock this risotto is actually built on.
Serves 4.
Soak the dried porcini in 300ml warm water for twenty to thirty minutes, until fully softened. Lift them out, squeeze out the excess liquid back into the bowl, and chop them roughly. Strain the soaking liquid through a fine sieve or a cloth-lined strainer to catch any grit -- dried porcini nearly always carry a little sand, and skipping this step is the most common reason this dish ends up gritty. Add the strained liquid to the warm broth.
Warm a little olive oil with half the butter in a wide pan, and cook the onion and garlic gently until soft. Add the chopped porcini, and cook for a few minutes more, until fragrant.
Add the rice, and toast for two to three minutes, stirring to coat it. Pour in the wine, and let it cook off entirely.
Begin adding the warm broth, a ladle at a time, stirring often and waiting for most of each addition to absorb before adding more. Continue for sixteen to eighteen minutes, until the rice is tender with a slight bite remaining.
Remove from the heat, and beat in the remaining butter and the Parmigiano until glossy and loose. Season with salt, and finish with chopped parsley.
If the finished risotto tastes gritty, the soaking liquid wasn't strained carefully enough before it went into the broth; next time, pour it slowly and stop well short of the last, sandiest bit at the bottom of the bowl. If the dish tastes surprisingly bland for something built around dried mushrooms, either they weren't soaked long enough to fully rehydrate and release their flavor, or -- more likely -- the soaking liquid was poured down the drain instead of into the pot, which throws away roughly half of what you paid for. And if the rice turns mushy, it was simply cooked past the point of a slight bite; pull it sooner next time, and trust the mantecatura's residual heat to finish the job.
A guest at one table informed his companions, at some volume, that mushrooms were simply a vegetable and there was really nothing more complicated to say about it. At the very next table, by total coincidence, sat a local and well-known professional mycologist, who said absolutely nothing at all and went on quietly eating her own porcini risotto with what Chiara later described as "the calm of someone who's decided this hill isn't worth fighting for."
Chiara has never told the loud guest who was sitting beside him. She considers it one of the few genuine mercies she's shown a customer all year.