La vieja is a very popular white fish in the Canary Islands. Fill a pan with water and bring it to the boil. Add then fish with a little bit of salt and parsley and cook until it is done. Take it out of the pan and put it on a plate to be served. Prepare the potatoes at the same time, wash them well, but do not remove the skin. Put them in another pan and add water to cover them, together with half a kilo of salt. Cook until the skin is wrinkled (ie, arrugada). Drain the potatoes and place them on the plate with the fish. A salad dressing is added individually to suit each taste. Usually a little chili pepper is added as well.