In a large saucepan over medium heat, melt the butter.

Add the chopped onion and minced garlic; sauté for about 3 minutes until fragrant.

Stir in the sliced mushrooms and cook until golden brown, approximately 5 minutes.

Add the Arborio rice, stirring to coat each grain with butter. Toast for about 2 minutes until slightly translucent.

Pour in the white wine, stirring constantly until mostly absorbed (about 2 minutes).

Gradually add warm vegetable broth, one ladle at a time, stirring frequently and allowing each addition to be absorbed before adding more (about 18-20 minutes total).

When the risotto is creamy and al dente, stir in grated Parmesan cheese and season with salt and pepper to taste.

Serve hot with extra Parmesan if desired.