Put the prepared fruits together with the cassis in a saucepan and mix with the preserving sugar.
Bring to the boil, stirring constantly, and let it simmer for 4 minutes. Do the gelling test towards the end of the cooking time, skim if necessary and pour hot into the prepared glasses. Close the jars immediately.
If you want children to eat the jam too, simply replace the cassis with 100g currants.