Spanish potato omelette

[Serves 4]

500g potatoes, peeled and sliced 5mm thick
1 medium onion, very finely chopped
¼ cup + 2 tbsp olive oil
6 eggs, beaten
sea salt flakes and freshly ground black pepper

1 Heat ¼ cup oil in a 20cm-wide heavy-based frying pan over a low heat. Cook the potatoes and onion for 15 minutes until the potatoes are tender but not brown.
2 Remove the potatoes with a slotted spoon and discard the oil.
3 Mix the potatoes with the eggs and season. Wipe out the pan with paper towel.
4 Heat 2 tbsp olive oil in the same pan over medium heat and add the egg and potato mixture.
5 Cook over a low heat until it is done around the edges, then place under a preheated grill. Cook until firm and golden.