Scrub the potatoes and put them whole in a saucepan. Cover with water—at least ½-inch above the tallest potato. Bring to a boil, reduce to a simmer and cook until the potatoes are tender when you poke them with a fork, about 20 minutes. Cool about 10 minutes, until you can handle them.

Meanwhile, dice the onion into ½-inch pieces. Over medium-low flame, heat 1 tablespoon of the oil in a large skillet. Add the onions and sauté until they are translucent, stirring often. Remove the onions from the pan.

When the potatoes have cooked and cooled, cut them in cubes about ½ to ¾ -inch square. Heat the remaining oil in the skillet over medium flame. Add the diced potatoes and stir them around to coat with the oil. Press them into the pan with a spatula. Sprinkle generously with salt and pepper and let the potatoes cook 5 to 10 minutes without stirring. The potatoes should get crisp and lightly golden on the bottom. When they are golden on the bottom, break them up with the spatula, stirring in the reserved cooked onions. Sprinkle the potatoes and onions again generously with salt and pepper and let them cook until the new bottom is nicely golden brown.