• 10 small potatoes
• 1/2 medium white onion
• 4 large eggs
• 2 large pinches of salt
• olive oil

1. Peel the potatoes and cut into thin slices. (A Japanese mandolin is an easy way to make uniform slices; otherwise a knife will do just fine).
2. Put the potatoes in a bowl, add one large pinch of salt, stir, and set aside.
3. Finely dice the onions and set aside.
4. Heat up some olive oil in a nonstick frying pan on high, just enough so that you'll be able to cover the potatoes. This pan will effectively be the mold for the tortilla, so make sure it's the size and shape you want. Important note: if you don't use a nonstick frying pan, it'll be practically impossible to invert the tortilla properly.
5. Add the potatoes to the pan and turn the heat down to low or medium-low.
6. After a few minutes add the onions
7. Turn the potatoes over every once in a while so that they cook evenly.
8. As the potatoes start ot cook more, take a wooden spoon and crunch the potatoes up into smaller pieces.
9. When the potatoes and onions are soft and lightly browned (but not too much), drain the oil into a colander with a bowl underneath.
10. Reserve some of this oil for later.
11. Beat the eggs in a bowl and add a large pinch of salt.
12. Add the potatoes and onions to the eggs and stir.
13. On medium-high, heat a spoonful or two of the reserved oil and add the egg/potato mixture.
14. Once the tortilla has cooked on the bottom (so that it's firm but not browned), you'll need to invert it.  This takes a bit of skill, but can be fun once you've gotten the hang of it, almost like throwing pizza dough up into the air - but easier, and Spanish.
15. Take a plate that's big enough to cover the surface of the entire frying pan plus at least a couple centimeters, turn it upside down, and lay it over the circumference of the pan.
16. With one hand hold the frying pan handle and with the other lay your hand on top of the plate.
17. In one quick, smooth motion you'll need to turn the frying pan over and the plate will then be on bottom*
18. Take the pan off the plate and put it back on the burner.
19. Very carefully slide the uncooked tortilla bottom from the plate into the pan and cook until done.
20. Then slide the finished tortilla onto a plate, cut into wedges.

Chef's Note: If the tortilla doesn't invert as it should and breaks apart on you, don't despair.You have a couple of options: You can put the tortilla back in the pan, add another egg, keep frying, and try inverting it again / Put it all back in the pan and mix and loosen it up like you were making hard scrambled eggs. Just tell everyone you were really making huevos rotos
Source: Rabbi Alan Ira Silver