1 tablespoon olive oil
2 large onions, finely chopped
750g / 1 ½ lb Pink Fir Apple Potatoes, peeled, cut and parboiled into 1cm / ½ in pieces
250g/8oz handful of fresh spinach, cooked and roughly chopped
10 free-range eggs, lightly beaten
Salt and freshly ground pepper
In a large heavy pan, fry-based, heat the butter and oil. Cook the onions slowly glassy and soft.
Add the potato slices and fry for two minutes.
Stir in the spinach.
Season the eggs with salt and freshly ground black pepper and pour the contents of the pan.
Cook over a low to medium heat: It can take up to ten minutes until the egg is enough to flip the tortilla is set, and when the heat is too high, the soil burn before the middle is set.
Once the bottom is browned nicely and the center has set, it is time to reverse it. This is done with a double flip: Put a plate (or the bottom of a tart tin) over the pan and turn it around once, so that the surface of the cooked tortilla on the bottom. Take a plate and turn it back so the surface is cooked on the top. Then put the pan back on the Pan Tortilla plate and flip one more time, so that the raw bit is now in contact with the bottom of the pan.
Replace the pan over low heat, until the tortilla is cooked through.
Serve hot, warm or cold, cut into slices or cubes.