In a large pot, bring the stock or water to a boil.
Turn the heat down to low and slowly pour in the polenta, whisking the whole time to make sure there are no lumps.
Cook on low, stirring for 15 minutes, then stir in the butter and cheese. Return to the heat and cook for another 10 minutes. Make sure you are stirring the whole time.
Taste the polenta. If it needs a little salt, then sprinkle some in and give it a stir. Cover and let it stand for 5 minutes.