In a large skillet or saucepan, heat the olive oil and 1 tablespoon of butter over medium heat. Add the chopped onion and sauté until translucent, about 3-4 minutes. Add the minced garlic and cook for an additional minute.

Cook the Mushrooms

Add the sliced fresh mushrooms to the skillet. Sauté them until they are tender and have released their moisture, about 5-7 minutes. Season with salt and pepper to taste.

Toast the Rice

Add the Arborio rice to the skillet, stirring to coat the grains with the oil and butter. Cook for about 2 minutes until the rice is slightly translucent.

Add Broth Gradually

Pour in 1 cup of the warm vegetable broth, stirring frequently. Allow the rice to absorb the broth before adding more, continuing this process until the rice is creamy and al dente, about 18-20 minutes total.

Finish the Risotto

Once the rice is cooked, remove the skillet from heat. Stir in the remaining tablespoon of butter and the grated Parmesan cheese. Adjust seasoning with salt and pepper as needed.

Serve

Garnish the risotto with freshly chopped parsley and additional Parmesan cheese if desired. Serve immediately.