Boil the potatoes in a pot with the 4 cups of water and the salt. Once they are ready, pour cold water over them. Wait a while and peel.
Pour them into a bowl and mash them. To the potatoes, add the butter, 1 egg and finely chopped onions. Make patties from the mixture.
Whisk the other 2 eggs. One by one, dip the patties in eggs, then in breadcrumbs, eggs again and then place them in a pan, to fry on both sides.