1. To make the Spanish omelette, peel the three potatoes and then cut them in half, then into even quarters.
2. Slice the potatoes so that they are approx. 1cm thick. If they are too thin, they will over cook and if they are too thick, they will undercook, so this part is very important!
3. Put a medium size deep fry pan on the stove at a low heat. Add a generous serve of extra virgin olive oil and leave to warm up.
4. Once the oil is nice and warm, add the slice potatoes in and leave to simmer for up to 5 minutes.
5. Peel the onion and slice it into thin strips then add these to the pan also.
6. Leave the potato and onion to cook through until they start to soften.
7. In a separate mixing bowl, whisk 5 eggs really well.
8. Pour the egg mixture into the pan and carefully move the mixture around using a spatula so that the egg gets through.
9. Keep moving the mixture for the Spanish omelette around sightly and ensure the edges are not stuck to the side of the pan by slightly sliding the spatula down and around he whole tortilla.
10. Leave it to cook for around 10 minutes.
11. Get a large, flat dish and lay it down over the top of the fry pan. Holding the fry pan in one hand and placing your hand flat on top of the bottom of the dish, flip the pan so the Spanish omelette falls on to the dish and the pan is empty.
12. Transfer the raw side if the Spanish omelette onto the pan and leave to cook for another 10 or so minutes (depending on your preference).