Step 1
Peel and slice 5 medium potatoes, about ¼ in (5mm) thick. Put about 10 fl oz (300ml) of olive oil in a deep-sided ovenproof frying pan (preferably nonstick), then add the potatoes, and cook at a gentle simmer for about 15 minutes, or until the potatoes are soft when you poke them with a sharp knife.
Remove the potatoes with a slotted spoon and put them in a large bowl to cool.

Step 2
Halve, peel, and quarter 3 medium onions, and slice to make crescent moon shapes. Pour most of the oil out of the pan (you can sieve and re-use), and add the onions and a pinch of salt. Cook over low heat until soft and beginning to caramelize.Add to the potatoes and leave to cool.

Step 3
Whisk 5 eggs with a fork, then pour into the cooled potato and onion mixture, season with sea salt and freshly ground black pepper, and combine gently so all the potatoes get coated, trying not to break them up too much. Preheat the oven to 400°F (200°C). Heat 1 tablespoon of the olive oil in the frying pan until hot, then carefully slide the mixture in, spreading it evenly so it covers the base of the pan. Reduce the heat to low-medium and cook for 6–10 minutes, or until almost set.

Step 4
Cook in the oven for a further 10 minutes, or until set and golden. Alternatively, cook one side, then invert onto a plate and add back to the pan to cook the other side. Remove from the pan, leave to cool and completely set, then slice into wedges.
Serve warm or cold.