1 1/3 pounds unpeeled potatoes – such as round reds or long whites (about 4 medium), cut into 1/8-inch-thick slices
1/4 cup olive oil
1 large onion – thinly sliced
4 large eggs
1 1/2 teaspoon salt
1/4 teaspoon freshly ground black pepper
several drops hot red pepper sauce
chopped fresh parsley or chives – for sprinkling (optional)
Put the potatoes into a large saucepan with enough salted water to cover. Bring to a boil over high heat. Reduce the heat; cover and simmer for 8 minutes or until the potatoes are tender. Drain well.
Meanwhile, heat half of the oil in a large nonstick skillet over medium heat. Add the onion and saute for 6 to 8 minutes, or until soft and golden; remove from heat. Beat the eggs, salt, black pepper and hot pepper sauce in a large bowl. Add the onion and potatoes to the eggs, tossing until mixed well. (Its OK if some of the potato slices break.)
Preheat the broiler. Heat the remaining oil in the same skillet over medium-high heat. Spread the potato mixture evenly and press it down lightly. Reduce the heat to medium and cook for about 4 minutes, or until bottom is golden brown, shaking the pan back and forth once or twice. Place the skillet under the broiler. (If the skillet handle is not ovenproof, wrap it in triple thickness of aluminum foil before placing it in the oven.) Broil 4 to 5 inches from the heat for 2 to 3 minutes or until the eggs are set. Watch carefully! Slide the tortilla onto a serving plate and sprinkle with parsley. Cut the tortilla into wedges and serve hot or warm.