To prepare the mashed potatoes start by washing the potatoes well under running water, and boil them with the skin in salted water for about 40-45 minutes, depending on their size.
Check if the potatoes are cooked, by pinching them with a fork and then remove them from the pot and peel them when they are still hot, then cut it into pieces and put them in a blender or potato masher.
Put the mix in a pan over low heat, add salt and stir. Now add 8/10th of the butter and stir again until the butter will be distributed evenly.
Gradually add the hot milk, until you have a smooth puree, swollen and homogeneous. The mashed potatoes are ready, remove the pan from heat and serve immediately, then add the butter and garnish with the finely chopped chives.