In a large skillet, heat olive oil and butter over medium heat. Once shimmering, add sliced mushrooms, stirring occasionally for about 6–8 minutes until golden brown.

In the same skillet, add chopped onion and cook for about 3 minutes until translucent. Stir in minced garlic and sauté for an additional minute.

Stir in Arborio rice, ensuring each grain is coated, and cook for about 2 minutes.

Pour in dry white wine, stirring until mostly absorbed, about 2-3 minutes.

Gradually add warm vegetable broth, one ladle at a time, stirring frequently, until creamy and al dente, about 18-20 minutes.

Fold in sautéed mushrooms, remaining butter, and Parmesan cheese. Season with salt and pepper, and cook for another 2 minutes.

Remove from heat and serve immediately, garnished with additional Parmesan cheese and parsley, if desired.