Cut the mushrooms into quarters, then peel and chop the garlic.
In a pan, melt half of the amount of butter, add one tablespoon of olive oil, then add the mushrooms and garlic, and cook for about 5-7 minutes until the mushrooms release all their liquid and brown.
Remove the mushrooms from the pan and set aside.
In the same pan, melt the remaining butter, add the rest of the olive oil, then the chopped onion.
Fry the onion until translucent.
Rinse the rice under cold water until the water runs clear.
Add the rice to the onion.
Stir for about 30 seconds, then add one ladleful of stock at a time, and keep stirring until it's absorbed, then add more until you finish it up and the rice is cooked through and creamy.
Add the cooked mushrooms, salt, parmesan and black pepper, and garnish with freshly-chopped parsley.
Serve hot.