Heat butter and oil in a deep saucepan. Saute onions until just softened and then add in the garlic and mushrooms and saute for a couple of minutes.
Add in the rice and seasonings and let the rice toast for a minute or two.
Stir in broth of your choice and bring to a gentle boi. Reduce the heat and cover, simmering until the rice is tender and liquid absorbed.
Fluff the cooked rice with a fork and serve immediately.