Place the polenta flour in a large plate, add the finely chopped garlic and chopped parsley, then mix well
In a medium bowl, bit an egg white, a few drops of water and a pinch of salt with a fork for a few seconds, just incorporating a bit of air.
Slice the large mushrooms about 1 cm thick, place them in the egg white mix and then in the polenta, making sure to press down enough for the polenta to stick to both sides of the mushrooms slices, once all mushrooms are prepped, place the cooking olive oil in a large frying pan and heat up.
Place a little piece of mushroom in the pan, once it starts to fry, carefully place one by one the slices inside the hot oil living some space between them.
They should cook about 1 minute on each side, but check, lifting the first slice placed with the tongs, it should be a nice golden colour. If the mushrooms are colouring to fast, and turning too dark, move immediately the pan from the heat and let cool for a few seconds on the side.
Once the mushrooms are cooked on both sides, move on an other plate linen with some absorbent kitchen paper, adjust seasoning with a pinch of salt, serve hot