Peel and rinse well the potatoes. Cut them in quarters or chunks and place them in a medium sized pot with enough cold water to cover them. Add salt and bring to boiling point. Then lower the heat and continue simmering until fork tender, approximately 20-25 minutes.
Drain the cooking water, saving some if you like to make it creamier or for the vegan version. Add the butter, milk and cheese and start mashing until becomes a smooth paste.
Transfer onto the serving dish and sprinkle with black pepper or chopped parsley / chives. Eat it at one meal, it loses it taste after several hours.