In a 3-quart saucepan, bring 5 cups of water to a boil. Add the salt and the sugar. Then drizzle in the polenta in a thin stream, whisking constantly until all the polenta has been incorporated and the mixture is beginning to thicken. Remove the pan from the heat, switch to a wooden spoon, and continue to stir until the polenta is as thick as paste. Stir in the goat cheese. Cover the pan tightly with plastic wrap and set it in a warm place.