01 - Heat 1 tablespoon butter in a large saucepan over medium heat. Add the chopped onion and cook for 3 to 4 minutes until translucent. Stir in minced garlic and cook for 1 additional minute.
02 - Add sliced mushrooms and sauté for 5 to 7 minutes, stirring occasionally, until browned and softened. Season with salt and pepper.
03 - Incorporate arborio rice and toast for 2 minutes, stirring constantly until grains show slight translucency at the edges.
04 - Pour in dry white wine and stir continuously until mostly evaporated.
05 - Add a ladle of warm vegetable broth to the rice. Stir gently and cook until liquid is mostly absorbed. Repeat by adding broth one ladle at a time, stirring frequently and allowing absorption before next addition, for approximately 18 to 20 minutes.
06 - Taste the rice; it should be creamy and tender with a firm bite (al dente).
07 - Remove from heat. Stir in remaining 2 tablespoons butter and freshly grated Parmesan cheese until creamy and well combined.
08 - Drizzle truffle oil over the risotto and gently stir. Adjust seasoning with salt and pepper if necessary.
09 - Serve immediately, garnished with chopped parsley and additional Parmesan if desired.