Fry the onions in the butter until translucent, add the mushrooms, sweat for 2 minutes. Then add the rice, fry a little, add the bay leaf and pour a little hot broth on top. Don`t forget to stir. When the broth has evaporated, add the broth again until the rice is firm to the bite. Remove from heat, add parmesan and truffle oil, stir well and serve immediately. Season to taste with salt and pepper.
Instead of porcini mushrooms, mushrooms can also be used.