Soak the currants in a bowl of water for 10 minutes until swollen. Put the barberries in a separate bowl of water and soak for 5 minutes. Drain both and pat dry separately. Set aside.
Peel the orange, removing all the pith. Cut the peel into very thin strips, then transfer to a small saucepan. Add enough cold water to cover, then bring to the boil over a medium