Elderflower syrup.  Now is the time to make it!

Pick a sieve full of elderflowers, nice ones in full bloom. Shake them a bit in order to loose eventual bugs and spiders.
Snip of the flowers from the stalks into a bowl, add warm water until they are almost covered.
Let them infuse au-bain-marie for about 2 hours, strain through a sieve lined with cheesecloth.
Measure the amount of liquid and add the same amount of sugar (1 liter = 1 kg sugar).
Bring to a boil and stir until sugar is resolved. Add the peel and juice of 1 lemon and let it brew very softly for 30 minutes.
Fill into sterilized bottles and keep in the fridge.