In a saucepan, heat the vegetable stock and keep it warm on low heat.

In a separate saucepan, melt butter and sauté onions and garlic until translucent. Add the Arborio rice and cook for 2 minutes. Pour in the white wine and cook until absorbed.

Gradually add the warm vegetable stock, one ladle at a time, stirring constantly until the rice is cooked and creamy. This process will take about 20 minutes.

Stir in the sliced mushrooms, grated Parmesan cheese, salt, and pepper. Cook for an additional 5 minutes until the mushrooms are tender. Serve hot.