Start by cooking the new potatoes - place in slightly salted water, bring to the boil and cook for 10-15 minutes until tender.
Prepare the rest of the ingredients: peel and slice the onion, slice the potatoes, slice the chorizo sausage if needed (I used read cut chorizo chunks), break the eggs into a bowl and beat.
Heat the oil in a frying pan then fry the onions for 2 minutes until beginning to soften. Add the potato slices and chorizo and continue to fry for 3 more minutes.
Preheat your grill to a medium/hot setting, then pour the beaten egg over the mixture in the frying pan and leave to cook for 6 minutes without stirring. Pop the omelette under the grill and cook for a further 2 minutes or until the omelette is cooked through.
Whilst the omelette is finishing off cooking, finely chop a few chive stalks for garnishing if wanted.
Tip out of the pan onto a plate, sprinkle with the chopped chives and cut into wedges to serve. We had ours with a leafy salad, cherry tomatoes and cucumber, yum!
Cool any leftovers quickly and store in the fridge, this omelette is delicious hot or cold so perfect for lunch boxes.