Chop the chorizo evenly in half. Dice one half roughly into cubes and thinly slice the other half of the chorizo.
Heat up the oil in a frypan on medium heat for a minute, add in the chorizo and onions. Stir and fry for a few minutes or until the onion softens. Take off the heat and leave to cool.
Preheat oven to 220°C (430°F) or 200°C (390°F) for fan-forced ovens. Lightly grease a non-stick 23cm (9in) baking dish/tin or ovenproof frypan. In the base of the pan place the potatoes, cooked chorizo and onions, make sure to spread it out evenly.
In a large bowl lightly whisk the eggs, add in the tomatoes, parsley, cheese, salt and pepper and mix gently to combine. Pour the egg mixture over the chorizo and potatoes, top it with the sliced chorizo. Bake for 15 to 20 minutes or until the egg has set.
Notes
(NOTE 1) Spanish Chorizo– I used prepackaged smoked and cured Spanish Chorizos, the ones found near the bacon section in the fridge.(NOTE 2) Eggs - I used large free-range eggs weighing approximately 58gm each (2oz). I prefer my omelette smooth and lush, so I only ever so lightly whisked the eggs. I find that over whisking the eggs results in a spongy and airy omelette. (NOTE 3) Cooked potatoes - Any variety of baked, boiled or steamed potatoes can be used as long as it's not too soft or mushy in texture.(NOTE 4) Cheese – I used Tasty cheddar cheese but you can use your favourite cheese as long as it melts nicely when heated. Parmesan, gruyère and all cheddar varieties are good choices.Leftovers - Allow the omelette to cool completely at room temperature and place it in a sealed container in the fridge, it'll keep up to 3 days.A Third-Party Application calculated the calories and nutritional information, so this is an approximate guide only.Cooking measurements are in Australian standard spoon and cup measurements.