The cured ham used in Alan Murchison's salad dish is a little bit special – it features the top grade of ham produced in Spain: jamón Ibérico de Bellota. This is not to be confused with the mass-produced Serrano hams. Make the avocado purée 2 to 3 hours before you want to use it to allow the flavours to infuse, and keep it in the refrigerator.