A dense moist cake of potato, egg, and onion, totally different from both the French omelet and the Mexican tortilla. It is more like a frittata than anything else.
1/2 cup olive oil
1 pound russet potatoes
1 medium onion, halved through the root and sliced thin
6 large eggs, lightly beaten
salt and pepper to taste
coarse salt for sprinkling the tortilla
Spanish olive oil for sprinkling the tortilla
1. Heat the oil in an 8-inch or 9-inch nonstick or well seasoned cast-iron skillet over moderate heat. Peel the potatoes and slice them very thinly (we like to use a mandoline or a less expensive slicing machine made from plastic). (Do not put the potatoes in water.) Add the potatoes and the onion to the skillet, and stir until they are completely coated with the oil. Reduce the heat to moderately low, and cook, stirring often so the vegetables will not color, until the potatoes are cooked through, about 12 minutes (they should remain separate). Remove the potatoes and onion with a slotted spoon to a baking sheet lined with paper towels, and let them drain.
2. Pour the oil out of the skillet and into a cup. Wipe out the skillet and remove any pieces of onion or potato stuck to it. Add 3 tablespoons of the oil from the cup back to the skillet. Carefully, transfer the potato mixture to a shallow bowl, pour the eggs over them, turning to coat well, season with salt and pepper, and let stand for 10 minutes.
3. Heat the oil in the skillet over moderately high heat until very hot, but not smoking, and add the potato and egg mixture, spreading the potatoes evenly. Reduce the heat to moderately low, and shake the pan often to prevent sticking.
4. When the top is no longer liquidy (about 10 minutes), cover the skillet with a plate and turn the tortilla out. Add 2 more tablespoons of the reserved oil, return the tortilla, cooked side up, to the skillet, and cook for about 5 minutes longer, or until cooked through and the underside is moderately browned. Let the tortilla rest until it comes to room temperature.
5. When ready to serve, cut into 6 wedges, and sprinkle each wedge with a little coarse salt and Spanish olive oil.
Omelet is not exactly the right word for this unique Spanish treat—but we don't have a better word in English to describe it. It's a dense moist cake of potato, egg, and onion, totally different from both the French omelet and the Mexican tortilla, more like a frittata than anything else. Soothing, homey, creamy, and satisfying, when first tasted it is often thought to contain cheese. But it doesn't; much of the creaminess comes from the slow cooking of the potatoes in the olive oil. Serve it as an appetizer before a Spanish meal, as a light lunch with a salad, or for brunch. Serves 6