1. Heat 1 tbsp oil in a large frying pan. Fry the mushrooms in two batches over a fairly high heat until browned. Season and set aside, reserving a few for serving.
2. Heat the remaining oil in a wide saucepan. Soften the onion for 5 minutes, add the garlic for 30 seconds, then stir in the rice until glossy.
3. Add the wine, if using, and let it reduce. Add hot stock a ladle at a time, stirring regularly and waiting until most of it is absorbed before adding more. Cook for about 18–20 minutes, until the rice is tender with a little bite.
4. Fold in most of the mushrooms, the butter and Parmesan. Add enough stock for a loose, creamy consistency, then cover and rest for 2 minutes.
5. Spoon into warm bowls. Sprinkle over 1 tsp black truffle powder, taste, and adjust. Top with the remaining mushrooms, parsley and black pepper.
