1½ cups caster sugar
1½ cups water
3 oranges, two thinly sliced and the zest only from the third orange
Put the sugar and water in a medium sized saucepan and bring to the boil, stirring to dissolve the sugar.
Add the orange slices and the zest and simmer gently for 25 minutes or until the pith and rind on the oranges is translucent. Turn the orange slices occasionally and shake the saucepan so the syrup is evenly covering the oranges. Cool then transfer to a sealed container. The oranges will keep in their syrup for several weeks in the fridge.