Pour the olive oil into a large skillet, heat to medium, and place the potato slices in the pan, but do not let them overlap as they’ll stick together and not cook evenly. You’ll probably need to do these in two batches.

The potatoes are ready when they start to break apart a little when handled. Take them out of the pan and put them onto absorbent kitchen paper.

You can cook the onions now in the same oil after cooking the potatoes. Cook the slices over a low heat until translucent. Add some salt at the end of the cooking process – it really brings out the flavour.

Break the eggs into a large bowl and beat lightly, then place the potatoes and onion into the mix, covering them with the egg mixture. Leave for 15 minutes.

Place the mix in a 23cm (9-inch) skillet over low heat, making sure all the pieces of onion and potato are covered as much as possible.

After 15-20 minutes check the bottom of the tortilla for doneness. If it’s done, it should be a golden colour and the top of the tortilla should be reasonably firm but still ‘wobble’ a little.

Place a plate that fits the skillet over the top of the skillet and invert. The tortilla can now be carefully slid back into the skillet to cook the other side for around 5 minutes.

You’re done! Rest it a little as tortilla is usually served warm, not hot.