Peel and wash the potatoes, cut them lengthwise into slices and fry them in 2 tablespoons of oil for about 10 minutes at a mild heat. Peel onions, cut into rings and add to the potatoes. Heat 2-3 tablespoons of water in a small saucepan, add the frozen spinach, cover and let it melt for about 10 minutes.
Season the potatoes with salt and pepper and push them together in the pan. Heat the remaining oil in the pan, break the egg and fry in the pan, sprinkle with salt and pepper. Sprinkle spinach with nutmeg and push together a little.
Add the spinach to the pan.