For me as a South African, polenta is a fancy Italian name for pap.  My entire family grew up with pap.  It was a household staple.  We had it as a hot breakfast porridge with milk and sugar or thickened to a consistency of playdough to be drenched in the fats of the BBQ meats which we called braaaivleis.  I'm salivating just writing about pap and vleis. This umami-rich mushroom polenta is an "upscale" version of pap and unlike pap that needs to be accompanied with something else, this dish can be eaten on its own.  

Polenta or pap is usually made with corn meal.  Corn meal should not be confused with corn starch.  Corn meal is corn that has been dried and processed.  There is white corn meal and yellow corn meal.  In the US, it is difficult to find the white cornmeal which was readily available in South Africa.

Tips for making Umami-rich Mushroom Polenta.

Mushrooms.

Use fresh mushrooms that you enjoy eating. When sautéing the mushrooms, add a combination of butter and olive oil into the skillet.  The combination of the different oils allows you to benefit from the butter taste but also increase the smoke point of the fat.  The smoke point is the temperature at which the fat burns.  Since butter has a low smoke point and burns quickly, by combining it with olive oil, the combined oils can reach a higher temperature to sauté the ingredients.

When sauteing mushrooms, if you are making a large quantity, do not overcrowd the skillet as this prevents the mushrooms from browning but rather it just steams, resulting in grey mushrooms!  Stir frequently to allow the moisture to evaporate and prevent the moisture from accumulating.  Remember to set aside a few mushrooms for the garnish.

Cornmeal

Cornmeal is a grain.  It is not corn starch.  Corn starch is usually used as a thickening agent.  Corn starch will not work for polenta!

Hydrating the corn meal in water for at least an hour helps to achieve a smoother consistency as the corn meal is then completely hydrated before cooking.

When cooking the polenta, the corn meal will continue to absorb water and thicken.  The longer the polenta cooks, the thicker it will become.  When the polenta reaches the consistency that's to your liking, add the mushrooms and butter.  When plating, garnish with the extra mushrooms and chopped chives.  The best way to chop chives is to use a herb cutter. This allows you to cut herbs uniformally.  

Enjoy and bon appetit!