• 2 tablespoons olive oil
• 2 medium onions, finely sliced
• 1 bay leaf
• 500 g cypress potatoes, peeled and cut into 2cm chunks
• 1 teaspoon salt
• 6 large eggs
• 1 tablespoon fresh rosemary, finely chopped
• ½ teaspoon black pepper
• 500 ml vegetable oil, to deep fry

First make your sweet onions. Pour the olive oil in a frying pan over low heat. Add the sliced onion and bay leaf and cook for 40 to 45 minutes, stirring occasionally, until the onions have reduced and are completely soft and lightly browned. You’ll end up with about four heaped tablespoons of sweet, caramelised onions. Set aside to cool.

Throw the potatoes into a bowl and mix with the salt. Set aside for ten minutes. Heat the vegetable oil in a deep pan over a high heat (140°C) – test it’s hot enough by dropping in a piece of potato which should start sizzling immediately. Deep fry the potatoes for 12 minutes or until golden and tender, then drain and leave to cool for at least 15 minutes. At this point preheat your oven to 180°C (160°C fan).

Whisk the eggs in a mixing bowl and add the cooled sweet onion mixture, rosemary and black pepper. Throw in the fried potato pieces and mix well. Line a deep baking dish and pour in the mixture.

Bake for 25 to 30 minutes, or until the tortilla is golden brown on top and cooked in the middle. Test it’s done by inserting a small knife or skewer in the centre – if it comes out clean your tortilla is ready. Cool for ten minutes before serving.