Spanish Truita (potato omelete)

Ingredients
4 eggs
3 potatoes
1 onion
salt/ cracked white pepper
olive oil
butter
optional: capsicum, zucchini, chilies, chiorizo

Method
1. First peel the potatoes and cut it into 1 cm thick slices slices. Do the same for the onion.
2.  Heat a non-stick fry pan over medium heat.  Add tsp olive oil, tbsp butter and onion.  Fry onion until it is translucent and it starts to caramelise.  Taking the time to do this step gives this dish a delicious depth of flavour from such simple ingredients.
3. Turn the heat to high.  Add the potatoes and enough boiling water to just cover them.  Simmer.
4.  While potatoes cook, break the eggs into a bowl and whisk gently.  Add salt and cracked white pepper.
5. As the water evaporates, test that the potatoes are tender.  If they are, pour off the remaining water, taking care to not pour out the onions and potatoes.
6.  If no oil remains in the pan, add a little.  Turn the heat down to medium and add egg.  Take care that the omelet does not stick to the fry pan by gently easing it off the sides with a plastic scraper or spatula.   Lean the saucepan back and forward while you separate it from the border. Egg will reach homogeneously all the omelet if you do it this way.
7. Once you think it is done (take less than 5 minutes), flip it, and shove it back in the frying pan in order to cook the other side. To flip it, use a plate or lid the same size as the fry pan.  Tip the pan over holding the lid on so that the omelet falls onto the lid.  Then gently push the upside down omelet back into the pan to cook the top. The most difficult part is flipping it, so be sure the frying pan is not too heavy and you have the right dish or lid and it is not slippery. I would recommend to check it beforehand. That is a clue step!

Here is a video I found in internet that shows the flip. Skip ahead about 3 minutes.