Heat a large frying pan (about 9 inches) over high heat. Add the oil and once hot, add the onions and potatoes. Fry until the potatoes are tender and crispy.

Drain the potatoes of the oil and place it in a bowl. Add the eggs and gently stir together. Meanwhile, heat the pan over medium low heat. Pour the egg and potato into the pan and season with salt and pepper.

With a spatula, gently move the potatoes around. Once the eggs start to set, stop stirring and allow it to cook. When the eggs on top have start to set, very carefully turn the omelet over onto a large plate. Slide the omelet back onto the hot pan. Cook for another minute until cooked through. Serve immediately.