For the currant syrup, wash and grate the currant and let stand with 200 ml water and 150 g sugar in a large pot for about 30 minutes.
In a half-closed pot (lid open a crack), slowly bring to a boil over low heat and boil for about 2 minutes.
Drain the currant mixture through a strainer lined with a muslin cloth, and when cool, squeeze the berries vosichtig with your hands through the cloth.
Boil the juice with the remaining sugar, the citric acid and 4 stalks of lemon balm.
Skim off the rising turbidity with a skimmer and fish out the lemon balm. Put two fresh stalks of lemon balm into a sterile bottle.
Measure out and pour in 500 ml of the hot currant syrup and close the bottle tightly immediately after filling.