In a small saucepan, heat the chicken stock and bring to a simmer. In a heavy-bottomed pot or pan, pour the butter substitute and sauté the pancetta and onions over medium-low heat for 5 minutes. Add the sliced mushrooms and sauté for another 5 minutes. Add the rice and stir to coat the grains with the butter substitute. Add the wine and cook for 2 minutes. Add 2 full ladles of the chicken stock mixture to the rice plus the saffron, salt, and pepper. Stir and simmer over low heat until the stock is absorbed, 5 to 10 minutes. Continue to add the stock mixture, 2 ladles at a time, stirring every few minutes. Each time, cook until the mixture seems a little dry before adding more of the stock mixture. Continue until the rice is cooked through, but still al dente, about 25 to 30 minutes in total. When done, the risotto should be thick and creamy in consistency. Remove from the heat and stir in the Parmesan cheese. Serve hot in bowls with extra cheese.