Place a heavy saucepan over high beat. Add water and bring to a rapid boil. Add the salt and, while stirring continuously with a long-handled wooden spoon, gradually add the polenta in a thin, steady stream until all has been incorporated.

Reduce heat until the mixture bubbles occasionally. Continue to cook, stirring constantly, until thick, smooth, and creamy, 20-25 minutes; be careful to scrape the bottom and sides of the pan frequently to avoid sticking or lumping. The polenta will start to come away from the sides of the pan and be stiff enough to hold the spoon upright.

Remove from heat and stir in the butter, a few cubes at a time, until fully .incorporated. Then stir in 1/2 cup of the Parmesan cheese. Return the pan to the heat, continuing to stir, until the polenta is piping hot; just a few secondd.

Transfer to a warmed bowl or platter and serve at once.