Polenta is an Italian dish comprised of coarse ground corn with additions of cheese, butter or other ingredients. In some versions the cornmeal is boiled, allowed to cool and cut into squares then grilled, broiled or even baked. The term "polenta" is also used to refer to the ground cornmeal used to prepare the dish.
Polenta is easy to find in the U.S and is sold in many well-stocked grocery stores. You can even find it precooked and formed into a plastic covered tube. Just slice the polenta and use as you would freshly prepared. This can be a real time saver.
If you don't have polenta meal then the best substitute would be to: