Rinse 5 large elderflower umbels and place in a sealable pot. To do this, add the juice of 3 lemons, rub in a little lemon peel and make up to 1 liter with water.
Cover and leave the pot to stand for 1 day, then drain through a hair sieve.
Boil 700 ml of the liquid with the amount of preserving sugar according to the instructions that is normally provided for 1 liter of fruit juice, otherwise the jelly will not set.
Pour hot into glasses and close tightly. After sealing, turn the jars upside down for 5 minutes.
Note: Do not make more than double the amount at once, otherwise the cooking time will be too long. If the jelly sugar is heated for longer than 7-9 minutes, the jelly will no longer solidify, but will remain liquid.