In Spain, the word tortilla means omelette. Spanish tortilla or tortilla de patatas is basically an omelette that is layered with potatoes and onions. The potatoes and onions are fried in oil before being stirred hot into the egg mixture so that a creamy sauce forms. Once you’ve made your thick, eggy mixture, you’ll pour this into a pan and continue to cook until golden on the first side. After golden, you’ll need a plate slightly larger than your pan to flip your tortilla and fry the other side. Tortilla isn’t necessarily served hot and it keeps well over time. You can make your tortilla as hefty as you’d like, but good luck flipping it if it’s over 1.5 inches thick.
Once your tortilla is fully cooked and golden on each side, place it on a plate to cool. Most tortilla is served at room temperature as pincho (a small snack).
Tortilla de patatas is a signature dish of Spanish cuisine. Because this is such a beloved old dish, there are many origin stories and many versions. Tortilla de Betanzos is a particularly popular type, which is a runnier, yolker, and does not contain onions.
There’s also a popular hack of using storebought potato chips for making tortilla espanola quickly and easily, rather than taking the time to fry potatoes and onions.