Elderflowers are profuse in Slovakia, and are also picked to make this simple floral syrup, usually mixed to make drinks.
Pick elderflower florets, preferably ones that haven't been rained on as more pollen will make a stronger tasting syrup. Cut close below the main stem.
Fill a large container with water and the juice from three lemons (this replaces the citric acid many use as a preservative). Put in the flowers, and let sit covered for between 24-48 hours. Mine sat about 36 hours.
Strain the water through a sieve into a 4 litre pot and stir in sugar. Warm the liquid over medium heat until sugar is dissolved. You can thicken the syrup by letting it reduce (evaporating the water) but don't let the syrup boil.
While hot, you can can the syrup to preserve it. You can also let the mixture cool, then freeze it. It also keeps in the fridge for a number of weeks.