Steps
1. In a saucepan, heat the vegetable broth and keep it warm over low heat.
2. In a separate pan, heat olive oil over medium heat. Add the chopped onion and sauté until translucent.
3. Add the minced garlic and sliced mushrooms, cooking until the mushrooms are tender.
4. Stir in the Arborio rice, allowing it to toast for 1-2 minutes until slightly translucent.
5. Gradually add the warm vegetable broth, one ladle at a time, stirring continuously until the liquid is absorbed before adding more.
6. After about 15 minutes, when the rice is creamy and al dente, stir in the chopped spinach and cook until wilted.
7. Remove from heat, and stir in the Parmesan cheese and butter (if using). Season with salt and pepper to taste.
8. Serve warm, garnished with extra Parmesan if desired.