Heat a medium, non-stick frying pan. Add the potatoes and onion and sauté for 6 mins or until pale golden. Add the chorizo and continue to sauté for 4 mins until the chorizo begins to colour. Stir in the spinach and cook until just wilted.
Beat the eggs with seasoning and the paprika. Pour the eggs into the frying pan, give everything a good stir, shake the pan to level the surface, then cover with a baking tray or plate and cook for 5 mins until most of the egg has set.
Preheat the grill, sprinkle the cheese over the tortilla, and pop it under the hot grill. Cook for a further 3-4 mins until the top is golden and the egg set. Leave to cool in the pan for 5 mins before transferring to a board and cutting into wedges. Serve hot, warm or cold - it's always delicious!