Pick the lilac at the beginning of flowering (when the flowers start to open and concentrate the fragrance). Avoid using lilac that has been in bloom for a long time as the flowers will not taste as good.
Gently shake the bunches, then remove the stems, taking care to keep as little stem as possible (this gives a bitter taste).
Place the flowers on a large tea towel and leave them for a few minutes until the remaining insects have gone...
Then place the flowers in a big bowl.
Boil the water and pour it over the flowers with the lemon juice. Cover with a cloth and leave to soak for 15 minutes.
Using a cheesecloth (or a fine sieve) placed over a saucepan, filter the preparation. Press the flowers with the back of a spoon to squeeze out the juice. This will give the syrup more colour and flavour.
Add the sugar to the pan and bring to boil and let it boil on a low heat for 15 minutes.
While the syrup is boiling, sterilise a glass bottle in a large pot of boiling water for 10 minutes and then place it upside down on a clean cloth.
When the syrup is ready, pour it immediately into the sterilised bottle and close.
Store in the refrigerator. The syrup can be kept for several weeks.