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