Creamy Polenta with Parmesan Cheese

Bring the water and milk to a boil in a heavy-duty sauce pan or small Dutch oven. Stir in the salt.
Gradually sprinkle the polenta into the pan while whisking at the same time. Turn the heat to a very low simmer, cover and continue to cook the polenta for 25-35 minutes, until it's thick, fluffy and begins to pull away from the sides of the pan. Stir frequently so it doesn’t stick to the bottom of the pan.
When it's done, remove from the heat and stir in the butter, cheese and additional salt to taste if needed.
Serve warm, sprinkled with rosemary and additional cheese, if desired.