Saffron potato tortilla

Place the saffron strands in a bowl and cover with the boiling water. Set to one side.

In a heavy-based, non-stick frying pan, heat 1 tablespoon of olive oil and the butter. Add the onion and gently fry until golden and soft.

Add the potatoes, cover with a lid and cook for 20 minutes until the potatoes are very soft.

In a large bowl, beat the eggs and mix in the saffron with its soaking water.

Add the cooked potatoes and onions to the eggs and season well with freshly ground black pepper.

In the frying pan, heat the remaining olive oil. Pour the potato and egg mixture into the hot frying pan, tilting the pan to spread it evenly. Fry for 2 minutes until the tortilla is just set.

Invert a large baking sheet over the pan and quickly turn out the tortilla. Then gently slide back into the pan and cook for a further 30 seconds to 1 minute on the other side.

To serve, turn out immediately onto a serving dish. Sprinkle with rock salt, cut into wedges and serve with a spinach, broad bean and tomato salad.