Heat the oil in a sauté pan over medium heat and gently cook the mushrooms until they start to sweat. Add the shallots to the mushrooms and continue cooking until the natural liquid from the mushrooms has reduced to nothing. Remove the mushrooms and shallots from the heat and add the brandy. Be sure to do this off the fire to prevent flambé. Place the pan back on the heat and reduce by half. After brandy has reduced, add the chicken stock and reduce by three-quarters. Season the mushroom ragout with salt.
Remove from the heat and reserve half of the cooked mushrooms. With the other half of the mushrooms and the liquid, blend in the food processor until smooth. Set aside the reserved mushrooms and puree for later.
In a heavy gauge stainless steel saucepot, heat the vegetable oil and sweat the onions until soft and translucent. Add the rice and gently toast to coat each granule in the oil, 3 to 4 minutes. Season with a pinch of salt. Add the white wine and with a wooden spoon continually stir until the rice absorbs the wine.
Slowly start to add the warm chicken stock to the rice half a cup at a time, until the rice is cooked and no stock remains. Make sure to continuously stir the rice to ensure it cooks evenly, doesn’t scorch, and most importantly, gets creamy. Add the set-aside purée mixture to the rice and bring it back up to temperature. Gently fold in the white truffle oil. Adjust seasonings if necessary. Serve risotto on individual plates or family-style and top with reserved mushrooms. Garnish with roasted tomato if desired.