Remove the papery husk from the physalis berries and rinse and halve the berries.Squeeze the lime and orange. Put the berries, the juice, the jam sugar and 100 ml water in a pan. Bring to the boil. Leave to simmer gently on a low heat for about 10 minutes. Pour the jam into a spotlessly clean jar. Put on the lid, turn the jar upside down and leave to cool. Tip: The jam can be stored for 6 to 9 months unopened.