In a medium-size heavy saucepan, heat the peanut oil. Over medium-high heat, saute the onion and garlic just to soften, stirring all the while, 3 to 4 minutes. Add the rice and continue to stir, using a wooden spoon, coating the rice with the oil and onion.
Deglaze with the white wine and cook until the liquid is absorbed, stirring often. Pour in enough mushroom and/or chicken stock to cover, about 3 cups, and cook, stirring often, until the liquid is absorbed.
Meanwhile, in a medium skillet, heat the olive oil. If the mushrooms are large, cut them into bite-size pieces and saute over medium-high heat just to soften, 3 to 4 minutes.
Pour 3 cups of stock into the rice, turn the flame to high, and stir in a large pinch of salt and the tomatoes. Stir until almost al dente. Stir in the mushrooms and the remaining 1-cup of stock, as necessary. Remember that the risotto should be creamy, not runny. Remove from the flame and vigorously beat in the chilled butter and 1/2 cup of the Parmesan until completely dissolved. Stir in the parsley, and season with salt and pepper to taste. Serve immediately.