Do not wash the cones, just shake them out very well to remove any creepy-crawlies.
Mix the water with the citric acid and pour over the cones. Leave in a closed container in a cool, dark place – preferably in the refrigerator – for 24 hours.
Strain the syrup through a fine sieve. Then mix with the grain and sugar until the sugar is completely dissolved.
Fill the liqueur into bottles: It is ready to drink immediately.