Make up the pizza base mix by mixing with the lukewarm water and knead for 4–5 minutes or until smooth. (Alternatively, follow the packet instructions.) Roll out the dough to make a 30 cm (12 inch) circle and set aside to rest for 8 minutes.
Heat a large dry frying pan until hot and carefully lower the pizza base inside. Cook over a medium heat for about 10 minutes, turning once, until lightly golden.
Meanwhile, make the pizza sauce. Mix the tomato purée, ketchup, oil, oregano and a pinch each of salt and pepper. Spread thinly over the pizza base in the pan and scatter over the chorizo and mozzarella. Continue to cook for a further 2–3 minutes, then place under a grill preheated to a medium-hot setting for 1–2 minutes until melting and bubbling. (If you do not have a grill, cook the pizza base for 4–5 minutes until 1 side is golden. Flip over, top with the sauce and toppings, then cook for a further 6–7 minutes until the base is golden and the cheese is melting.)
Cut into slices and serve topped with the rocket leaves.