A staple of Spanish kitchens, tortilla de patatas is a humble yet deeply satisfying dish made with just a few ingredients: eggs, potatoes, and olive oil. Some swear by the sweetness of slow-cooked onions, while others insist on keeping it pure — here, you decide. Served warm or at room temperature, it’s perfect for breakfast, lunch, or a late-night snack. A bold aïoli on the side makes it even more irresistible. This one really is Spain’s national dish.

Prepare the Potatoes (and Onions, if using) Peel and slice 600g (about 4 medium) waxy potatoes into thin, even slices — about 3–4 mm thick. If using onion, slice 1 medium onion into thin half-moons. A mandolin would come really useful here! Heat olive oil (or vegetable oil, enough to submerge the potatoes — around 500 ml) in a deep frying pan over medium-low heat. Add the potatoes (and onions if using), and gently poach — not fry — them for about 20–25 minutes, stirring occasionally until tender but not browned. Drain the potatoes and onions in a sieve or slotted spoon, reserving a bit of the oil for cooking the tortilla.

Beat the Eggs In a large bowl, beat 6 eggs with a generous pinch of salt. Fold the hot potatoes into the eggs. Let the mixture sit for 10 minutes to allow the eggs to absorb some of the potato flavour.

Cook the Tortilla Heat 2 tablespoons of the reserved oil in a non-stick or well-seasoned pan (22–24 cm diameter) over medium heat. Pour in the egg and potato mixture and shake the pan to distribute evenly. Cook for 4–5 minutes, gently shaking the pan occasionally. The edges should begin to set while the centre stays soft and custardy. Now comes the tricky part: the flip. Place a large flat plate (or a flat pan lid) over the pan and carefully invert the tortilla onto it. Then gently slide it back into the pan to cook the other side for another 3–4 minutes, depending on how runny or firm you like it inside.

Nervous about flipping? No shame, many tortillas have ended on the stove top over the years, and there’s no need for that: you can always finish it under the broiler for 2–3 minutes instead. Just make sure your pan is oven-safe and keep an eye on it so it doesn’t overcook. Once cooked to your liking, slide the tortilla onto a plate and let it rest at least 5 minutes before serving.

Make the Aïoli In a bowl or small blender, combine 1 egg yolk (room temperature), 3 garlic cloves, grated or crushed, 1 tsp lemon juice or white wine vinegar and a pinch of salt. Start whisking (or blending), and very slowly drizzle in 200 g vegetable oil (neutral oil like sunflower or grapeseed). Whisk continuously until it thickens into a glossy, smooth sauce. Adjust seasoning to taste. If it’s too strong, mellow it with a touch more lemon juice or a splash of water. Serve. Cut the tortilla into wedges and serve warm or at room temperature, with a generous spoonful of aïoli on top. Perfect with crusty bread, salad, or a chilled glass of cider or vermouth.