In a medium pot, heat the broth and the reserved whole mushrooms to a simmer over medium heat.
In a large saute pan over medium heat add the olive oil and the onion. Sweat, stirring often for 5 minutes until the onion is soft and tender.
Add the diced mushrooms and cook another 2 to 3 minutes . Add the rice and stir to coat the rice with the onion and oil. Cook stirring often for 2 minutes. Add the wine to the rice and stir, scraping any bits from the bottom of the pan.
As the wine cooks off, add a large ladle of hot broth and continue to cook and stir. As the broth cooks off, add another ladle of broth. Continue this process of adding broth and cooking it off, stirring continuously for about 20 minutes or until the rice is al dente.
Season to taste with kosher salt and stir in the fresh thyme leaves. Serve hot with the whole mushrooms on top for garnish and a drizzle of truffle oil.
This nutritional information refers to each serving of the entire recipe and not just the products used as ingredients.