In a large saute pan, over medium heat, heat the oil. Add the onions. Season with salt and pepper, and cook, stirring. Saute until the onions are slightly soft, about 3 minutes. Add the stock and garlic
. Bring the mixture to a boil, reduce the heat to medium, and simmer for about 6 minutes. Add the rice and simmer for 10 minutes, stirring constantly. Add the mushrooms and continue to simmer, stirring constantly, until the mixture is creamy and bubbly, about 8 minutes. Stir in the butter, cream, cheese, green onions
, and truffle
for 2 minutes, stirring constantly. Remove from the heat. Spoon the risotto
in the center of each shallow bowl. Garnish
with the croutons and shaved truffles.