In a small saucepan, heat the butter over medium heat.

Add the chopped onion and minced garlic, and sauté for about 3 minutes until softened.

Add the Arborio rice to the saucepan and stir-fry for another 3 minutes.

Pour in the dry white wine or sherry and continue stirring until the wine is absorbed.

Gradually add the vegetable broth, a ladleful at a time, stirring continuously and waiting until each addition is absorbed before adding more.

This process should take about 15 minutes.

Once the rice is cooked and creamy, cover the saucepan and let the risotto simmer gently for about 15 minutes.

Remove from heat and let it rest for another 5 minutes.

Meanwhile, cook the sliced mushrooms in the remaining vegetable broth for about 3 minutes.

Then, remove them from the broth and stir them into the risotto along with the chopped parsley.

Heat the risotto for an additional 3 minutes, stirring occasionally.

Season the risotto with salt, pepper, and a splash of lemon juice to taste.

Optionally, sprinkle grated 20+ cheese over the risotto before serving.

Serve the mushroom risotto with cooked spinach on the side.