From  Nick de Toldi with edited comments from Mariano del Carril

Recommended proportions, for a 9 or 10 inch diameter pan

 INGREDIENTS

6 eggs (Mariano’s Rule 1: more egg is always better, so add two more.  Eggs makes your body good!

5 potatoes roughly of the size of the eggs  (Mariano says 3 of average American size)

2 onions of the same size, cut in small squares (Mariano says 1 of average American size)

olive oil

Marianno would add:

1 ½ t. kosher or sea salt

¾  t. freshly ground black pepper

¼ t. sugar

3 baking potatoes, (about 2 pounds), peeled and sliced into 1/8-inch rounds (you can use any kind of potatoes)

8 eggs, lightly beaten

½ c. julienned serrano ham, Spanish chorizo (or fried bacon, which I deny ever having used)

DIRECTIONS

Boil the potatoes for 15 minutes while letting the onions take colour in the pan in olive oil. TAKE COLOR, BUT NOT GOLDEN, YOU USE THE OIL TO BOIL THEM NOT TO FRY THEM, SO I NEVER HAVE MY ONIONS GOLDEN. THEY ARE COOKED SLOWLY IN THE OIL WITHOUT BURNING THEM.  Cut the boiled potatoes in slices and pass them in the pan in olive oil as well. Beat your eggs, season with salt and pepper.  SAME COMMENTS AS ABOVE FOR THE POTATOES IF YOU ARE GOING TO SLICE THEM, THEN THE COOKING IS SLOW AND NEVER FRY THEM, BOIL THEM IN OIL. BTW, I NEVER SLICED THE POTATOES BEFORE BUT AFTER I BOILED THEM IN WATER. THIS IS A MATTER OF TASTE, NOTHING ELSE!  

When the potatoes are sautéed, pour them hot with the onions in the beaten eggs and mix thoroughly (that is an important stage).   Mariano adds Rule No. 2:  I separate the yolk from the white (the big secret) and I start to shake the whites until they become a white foam. As soon as I have this foam I incorporate the yolks, salt (don’t be shy with salt), some cayenne pepper, pimenton, and chopped parsley. And Rule 3: I cook the potatoes and the onions separate. Potatoes I cook them whole and after they are cooked (not fully cooked actually) I cut them in small squares. Onions are also cut in small squares and when they are almost cooked I incorporate a full teaspoon of chopped fresh garlic and (I have not used this on the one you ate) chorizo (cut in small squares) Let the ingredients cool down Before mixing them since the egg can cooked earlier than you desire if you put the hot potatoes and onions right after cooked.

Put the pan on fire again with olive oil (MARIANO WOULD USE A DAB OF BUTTER HERE) and when very hot (MARIANO SUGGESTES MEDIUM), put the mixture of eggs, potatoes and onions. Mix until it becomes solid, and let harden for 6 minutes. Put the 1st clean plate on top of the pan, put your hand to maintain everything tight, and turn (collapse) in order to have your omelette in the plate, with the cooked side facing the sky ! Add (again) a bit of olive oil in the pan and when hot, make the omelette slip in it, in order to cook the uncooked side. Let it harden on fire for 6 minutes, and when done put the “tortilla” on the 2nd clean plate. THE AMOUNT OF TIME NEEDED FOR THIS VARY BUT, IN GENERAL, FOR ME AND MY RANGE IS MORE THAN 20 MINUTES PER SIDE. THIS IS SOMETHING THAT YOU WILL MASTER AS YOU DO IT, EACH RANGE IS DIFFERENT. In mine, the first side is between 20 and 30 minutes and the second side goes between 10 and 20 minutes (top, top).  Serve whenever suits you… now, or a couple of hours later (recommended) or even the next daytotally cold on a fishing picnic for instance. 

Cheers, Nick                    Ciao! Mariano