Lightly whisk the eggs in a small bowl. Season with salt and pepper.
Finely chop the spring onions, (chilli, if used) and the frankfurters. Grate the cheese and set aside.
Heat the oil in a small frying pan. Add the spring onion and frankfurters and fry for a minute or so, until the Frankfurter pieces start browning.
Add the eggs mixture, allowing it to spread out around the pieces. Cook for about 5 minutes over medium heat, or until the egg is almost set.
Sprinkle over the cheese and chilli pieces( if used), turn down the heat and the cook for a couple of minutes. Carefully fold the omelette in half with a spatula. Let the cheese melt completely, cut in half and serve.