01 - Heat 2 tablespoons olive oil and 1 tablespoon butter in a large heavy-bottomed pan over medium heat. Add the chopped onion and cook until translucent, about 3 minutes.
02 - Incorporate minced garlic and cook for 1 minute until fragrant.
03 - Stir in sliced mushrooms and cook for 6 to 8 minutes until softened and any released liquid evaporates. Season with salt and pepper.
04 - Add Arborio rice to the pan and stir for 2 minutes, allowing the grains to lightly toast and edges to become translucent.
05 - Pour in a ladleful of warm vegetable broth, stirring continuously until the liquid is mostly absorbed. Repeat by adding broth one ladle at a time, stirring frequently and permitting absorption before each addition. Continue this process for 20 to 25 minutes until the rice is creamy and al dente.
06 - Stir in the remaining 2 tablespoons butter and freshly grated Parmesan until fully melted and the mixture is creamy.
07 - Remove from heat, drizzle with truffle oil, sprinkle with chopped parsley, and adjust the seasoning with salt and pepper if necessary.
08 - Serve immediately, garnished with extra Parmesan and parsley.