Boil the potatoes in salted water until cooked then cut into mouth-sized chunks. These can be cooked ahead and stored in the fridge for up to 1 day.
Put the oil into a frying pan and cook the chorizo and onion together. When browned, remove and put into a roasting tin. Fry the cooked potato chunks in the red-coloured oil left in the pan. Spoon the potatoes into