Place water and sugar in a large pot and bring to a boil; stir until rock sugar is dissolved. Leave to cool completely. It is important to cool the syrup thoroughly.
Prepare a big glass jar (you can buy one from any provision shop) by washing it well and then drying it thoroughly.
Scatter raisins evenly on the base of the jar. Sprinkle both types of wine biscuits over the raisins. Pour in the cooled syrup slowly. Seal the jar lid tightly and allow the liquid to ferment and mature in a cool, dry and dark place for 100 days. Do not move the container during the fermenting and maturing period. If you do not follow this piece of grandmother´s lore, the whole process will not turn out well.