4 oz. unsweetened chocolate, finely chopped
3 tbsp. unsalted butter
2/3 cup water
1/3 cup sugar
6 tbsp. corn syrup
Pinch of salt
1 tbsp. rum (or vanilla extract)
Combine the chocolate and butter in a heatproof bowl set over a pan of simmering water. Heat slowly, stirring occasionally, until completely melted and smooth. Meanwhile, heat the water to boiling in a small heavy saucepan. When the chocolate and butter have melted, stir the mixture into the boiling water. Add the sugar, corn syrup and salt, and mix until smooth. Increase the heat and stir until the mixture comes to a boil. Adjust the heat so that the sauce is just maintained at the boiling point. Allow to boil for nine minutes, stirring occasionally.
Remove the pan from the heat and let cool for 15 minutes. Stir in the rum until smooth. Serve warm over ice cream.
Store in an airtight container in the fridge. To reheat, microwave in 15 second intervals, stirring until shiny and smooth.