Rinse the fruit in cold water and drain.
Pluck the currant from the stalks and remove the stalks and leaves from the strawberries. Cut the strawberries into pieces. Bring to a boil in a saucepan with a little water and simmer over low heat for 4 minutes.
Remove from heat and puree with a blender to a fine pulp. Continue to simmer for another 4 minutes.
Place a large strainer in a saucepan and line with a straining cloth (muslin cloth). Pour in the fruit puree and strain or let drain for at least 4 hours.
Measure 700 ml of juice and mix with the jelling sugar (2:1) and the Prosecco.
Boil for 4 minutes until bubbling and do the jelly test. To do this, drip some of the juice onto a cold plate. If it becomes solid, the jelly is ready. If not, let the mixture boil a little longer.
Immediately pour the jelly into prepared twist-off jars. Place on a tea towel with the lid down and allow to cool.