Wash the chicken liver in cold water, clean it well from the skins and then put it in a bowl with milk. Leave it in the fridge for 2 hours.
Prepare a pan, put the cube of butter and let it melt, then put the drained liver. Cover with a lid and leave on the right heat.
When they are almost done, cut the onion into scales and put it in the pan, leaving it to brown a little. Season with salt and pepper, grind the garlic and put it over the liver. Mix with a wooden spoon and then take everything out on a wooden bed.
Serve with polenta!