In a Medium Bowl, stir the risotto and ¼ cup of the Parmesan cheese to blend. In a heavy, large skillet, melt the butter and oil over medium-low heat. Add the risotto to the skillet and press into a 7-inch-diameter disc. Sprinkle the remaining 2 tablespoons of Parmesan cheese over the risotto cake. Cover and cook for 10 minutes, then uncover and continue to cook until the risotto cake is golden brown on the bottom and set around the edges, about 5 minutes longer. Using a large metal spatula, loosen the risotto cake from the pan and slide it onto a plate. Cut the risotto cake into wedges and serve.