Tradition has it that this liqueur must be made on the 24 June, the feast of St John. Put the walnuts in a large glass jar and add all the other ingredients. Cover the jar with a strong piece of paper, tie it on and make a small hole with a pin. Wrap the jar in thick black paper, and leave in the sun for 40 days. The black paper is to absorb as much warmth as possible on cooler days. After 40 days, filter the liqueur and put it in bottles. Seal them well.