These neat little parcels are an excellent way to use up leftover ham after Christmas. Once you get the hang of them, they're guaranteed to become a regular part of your repertoire, with all sorts of fillings.
Note Masa flour, also known as masa harina, is a form of cornflour, but regular cornflour doesn't work as a substitute. It's available from South American food stores such as Tierras Latinas and spice stores. Dried corn husks are also available from South American food stores, or you can use fresh husks from the greengrocer. Soak dried husks in cold water before using to make them pliable.