1. Combine the milk, chicken stock, butter, salt, white pepper, and mace in a large saucepan, and bring to a boil over high heat. Whisk in the polenta and stir continuously until the mixture begins to thicken. Then reduce the heat to medium-low and cook, stirring frequently, for 30 minutes, or until the polenta is creamy and tender.
2. Add the Parmesan and the mascarpone, and stir to blend. Remove from the heat and stir for 3 minutes to cool the polenta.
3. Serve immediately or keep warm until ready to use. (Leftover polenta is easily reheated in a small saucepan with a little water or milk to soften it.)
Yield: 4 to 6 servings