01 - Heat olive oil and 1 tablespoon butter in a large, heavy-bottomed skillet over medium heat. Add the chopped onion and cook until soft and translucent, about 3 minutes.
02 - Stir in the minced garlic and cook for 1 minute until fragrant.
03 - Add the sliced mushrooms and sauté until they release their moisture and begin to brown, 5 to 7 minutes. Season lightly with salt and pepper.
04 - Stir in the Arborio rice and cook, stirring frequently, until the grains are well coated and translucent at the edges, about 2 minutes.
05 - Pour in the white wine and cook, stirring, until the wine is fully absorbed.
06 - Begin adding the warm vegetable broth, one ladleful at a time, stirring frequently and allowing each addition to be absorbed before adding the next. Continue until the rice is creamy and al dente, 18 to 20 minutes.
07 - Remove from heat. Stir in the remaining 1 tablespoon butter, Parmesan cheese, and heavy cream. Adjust seasoning with salt and pepper.
08 - Drizzle with truffle oil and gently fold it in.
09 - Serve immediately, garnished with chopped parsley and additional Parmesan if desired.