1. Place the potatoes in a large saucepan and add enough cold salted water to cover. Bring to a boil over high heat, then reduce heat to medium-low and simmer until tender when pierced with a knife tip (about 25 minutes). Drain and rinse the potatoes under cold running water. Refrigerate until chilled, two or more hours (or overnight).
2. Peel the potatoes and cut them into small cubes. Heat the oil over medium-high heat in a large pan. Add the potato cubes and cook, stirring occasionally, until browned, about 10 minutes. Add half of the onion and cook, stirring often, until softened (about 2 minutes). Remove the potato mixture pan from heat and season with salt and pepper.
3. While the potatoes are cooking, prepare the tortillas for browning by spreading a light coating of butter on one side of each of the tortillas.
4. Meanwhile, whisk together in a bowl the eggs, 3/4 teaspoon of salt and 1/4 teaspoon of pepper until just thoroughly blended. Avoid over-beating. Return the pan with the potatoes to medium-low heat and add the egg mixture. Cook until the eggs begin to set (about 20 seconds). Stir with a heatproof spatula, scraping up the eggs on the bottom and sides of the pan and folding them toward the center. Repeat until the eggs are barely cooked into moist curds. Remove the pan from the heat and let stand for about 1 minute to allow the residual heat to finish cooking the eggs.
5. Fill the tortillas with equal amounts of the potato egg mixture, sprinkle with cheese and top with a spoonful of pico de gallo.

Pico de Gallo Instructions

1. In a non-reactive bowl, combine the tomatoes, onion, cilantro, lime juice and jalapeno.
2. Season with salt.
3. Cover and let stand at room temperature for at least 30 minutes or up to 3 hours.

To make a strictly vegetarian version of the tacos

1. Forego the eggs and cheese and add chopped or sliced portabella mushrooms and/or avocado.
2. Use extra virgin light olive oil to spread on the tortillas in place of butter.