1. In a small saucepan over medium heat, combine the sugar, water, strips of orange rind, and mint leaves. Bring to a boil, reduce heat, and simmer for five minutes, stirring occasionally until the sugar has dissolved. Remove from the heat and allow the syrup to cool for 20 minutes.
2. Remove and discard orange peels and mint leaves. Mix lemon juice and orange juice into the syrup. Freeze until very firm (overnight).
3. Remove the mixture from the freezer and blend in a food processor for 5 minutes until very creamy and smooth. Scoop into orange shells and freeze until ready to serve.
4. Garnish with mint leaves.