Serve the polenta immediately if you like it smooth and creamy or top it with sauteed mushrooms. To eat it fried, spread it into a baking dish, let it firm up, then cut it into squares to pan-fry.
In a medium saucepan, bring 4 cups water and cream to a boil. Add 2 tablespoons of the butter and the salt. Slowly stir in the polenta, reduce the heat to a simmer, and cook, stirring constantly, until thick and creamy, 15 to 20 minutes. Stir in the cheese, optional herbs, pepper, and remaining tablespoon of butter. Serve immediately or spread in a baking dish to firm up.