The sour cherries (only available from the end of June to the beginning of July - the really sour ones, which cannot be eaten raw and which look a bit glassy!) Are washed and the stems removed.
Then you put them in a large saucepan and add enough water to just cover the cherries. Simmer until the cherries are quite soft. This takes about 20 minutes. Attention, the mass likes to foam!
Then pour the juice through a sieve, throw away the cherries that have been caught and measure 3/4 liter of juice. Let it cool, add the citric acid and the preserving sugar and bring to the boil. Let a mint boil bubbly and then fill into glasses.