Step 1 of 4

Poach the potatoes in oil, do not fry them

Heat the oil in a 24cm non-stick pan over a medium-low heat and add the potatoes and onion with a teaspoon of the salt. Cook gently for about 20 minutes, turning them over now and then, until a slice crushes easily against the side of the pan.

— If they are coloring, the heat is too high. This is closer to confit than to frying, and browned potatoes give you a tortilla that tastes of chips.