1 Place the sugar in a litre of water and bring to the boil. Simmer for around 5 minutes until the sugar has dissolved.
2 Place the oranges on a perforated tray or a fine sieve over a baking tray. Cover with the syrup and leave to steep for around 12 hours.
3 Drain the syrup bring to the boil again and leave to cool slightly. Pour over the oranges again and leave to steep for another 12 hours.
4 Remove the oranges from the syrup and place on a wire rack to drain. Leave to dry for 1-2 days.
5 Melt the chocolate in a bain marie. Remove from the heat and dip the orange slices in it so that they are half coated with chocolate. Place on baking paper to dry.