Bring the sparkling wine to a boil with the flowers.
Add the lemon juice. Turn down the heat and let it simmer very gently for at least another 10 minutes.
Strain the lavender flowers. Add the preserving sugar. Boil the lavender jelly recipe again, stirring constantly.
After 4 minutes, do the jelly test. To do this, pour a small amount of jelly onto a cold plate. When the lavender jelly has the consistency you want, you can bottle it.
After filling, immediately put the lids on the jars. Put it aside and let it cool.