Preheat the oven to 350 degrees.

In a medium sauté pan, heat the olive oil over medium heat until shimmering. Sauté the garlic and onions until soft and transparent, 3 to 4 minutes. Add the mushrooms and sauté until golden brown, about 2 minutes. Season with salt and pepper.

In a separate saucepan, bring the stock to a boil. Add the rice, mushroom mix, and the hot stock to a 10-cup casserole or 9 x 13 inch baking dish. Tightly cover the baking dish with aluminum foil and place it in the center of the oven. Bake for 40 minutes or until most of the stock is absorbed and the rice is creamy.

Meanwhile, bring a large pot of water to a boil. Add the asparagus and simmer for about 4 minutes or until tender. Remove the asparagus from the simmering water and submerge it in an ice bath for about 1 minute to stop the cooking process and let it cool completely.

Remove asparagus from the ice bath with tongs and drain on a towel. Cut the tips off the asparagus and then cut the stems into 1/2-inch pieces. Keep the asparagus at room temperature.

When the risotto is done baking, stir in the asparagus and re-cover the dish with foil for one minute to heat the asparagus through. Stir in the butter, mascarpone and Parmesan cheeses, and truffle oil.

Serve immediately.