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 oil. Simmer 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.
Preheat the oven to 350 degrees F. Line a cookie sheet with parchment paper. In a food processor or blender, blend the egg and lemon juice together for 10 seconds. White the processor running, slowly pour in the vegetable oil through the feed tube. The mixture with thicken. Add the mustard, hot pepper sauce and salt, and pulse one or twice to blend well. Spoon the mixture into a small bowl and add the cheese, pepper, and truffle oil. Mix well. Cut each slice of bread diagonally into two triangles. Spread about 1 tablespoon of the mayonnaise mixture on each triangle. Place the triangles on the baking sheet and bake until lightly golden, about 15 minutes. Serve warm.
Yield: 20 croutons