Warm the broth in a saucepan on medium heat; keep warm but not simmering.
Add butter and oil to a pot over medium heat.
Add the onions and mushrooms; cook until just tender, then add the garlic. Cook 1 minute longer.
Add the rice and toss to coat with the oil and butter (making sure oil gets onto every grain of rice if you can).
Add 1 ladle full of the broth and stir until it absorbs.
Repeat this process until you have used almost all of the broth - it should take about 20-25 minutes.
When you add the last ladle of broth, let the stock absorb halfway and then add your cheese.
Let it absorb until it is creamy and thick, but not soupy. Season with salt and pepper to taste. Stir in the parsely before serving.