First put the sugar and water in a small saucepan and stir over low heat until the sugar has dissolved. Then stir in the chocolate in portions, allowing each portion to melt before adding the next. Add the butter little by little and stir in.
Important: the sauce must not boil!
Stir in the orange juice and remove the pan from the stove.
You can serve the sauce straight away. You can also let them cool down, put them in a freezer and freeze them for up to 3 months.