01 - Heat olive oil and 1 tablespoon butter in a large heavy-bottomed pan over medium heat. Add diced onions and cook until translucent, about 3 to 4 minutes.
02 - Stir in minced garlic and cook for 1 minute until fragrant.
03 - Add sliced mushrooms and cook, stirring occasionally, until softened and liquid evaporates, approximately 6 to 8 minutes. Season lightly with salt and black pepper.
04 - Add Arborio rice and stir to coat grains with the mushroom mixture. Toast the rice for 1 to 2 minutes until edges become translucent.
05 - Pour in the white wine and cook while stirring until most liquid is absorbed.
06 - Begin incorporating warm vegetable broth one ladleful at a time, stirring frequently. Allow each addition to be absorbed before adding more. Continue until rice is creamy and al dente, about 18 to 20 minutes.
07 - Remove pan from heat. Stir in remaining butter and grated Parmesan cheese. Adjust seasoning with salt and pepper to taste.
08 - Plate the risotto, drizzle with truffle oil, and sprinkle with fresh parsley before serving.