Set a handful of the sliced mushrooms aside for the optional garnish.

In a large nonstick skillet, heat the oil over medium high heat. Then add the remaining mushrooms and cook, stirring occasionally for about 3 minutes until they just start to soften. Season with the salt and pepper then remove from the skillet and set aside.

Add 2 tablespoons butter to the skillet and reduce to medium heat. Once the butter is melted, add the onions and cook, stirring occasionally for about 2 minutes until they start to soften then add the garlic and cook 1 minute.

Add the rice to the skillet and stir. Add the mushrooms with drippings, and the broth to the skillet and bring to a simmer. Cover and cook for about 15 minutes on low until the liquid is absorbed.

Optional garnish: While the rice simmers, heat a large heavy skillet over medium high heat. Once hot, add the remaining 1 tablespoon butter, followed by the handful of mushrooms you reserved. Saute 5-8 minutes, flipping occasionally, until deep golden brown.

Remove rice from the heat and fluff the rice with a fork, cover and leave for 5 minutes. Taste and adjust seasoning. Garnish with fresh chopped parsley and sauteed mushroom garnish and serve immediately.