1. Thinly slice the oranges and remove all pips. Place in a large saucepan with the water.
2. Simmer gently uncovered for 1 ½ hours or until the peel is tender and the mixture thick.
3. Add the Jam sugar and heat gently, stirring continuously until dissolved. Do not allow to boil. Add the butter and while continuing to stir, increase the heat until mixture starts to boil. Boil for 4 minutes.
4. Remove from the heat and leave to cool for 3 – 4 minutes before placing into jars.