1 to 2 tablespoons dark rum or 1/4 teaspoon rum extract
How to Make It
Cook sugars, whipping cream, and butter in a heavy saucepan over medium heat, stirring constantly, until butter melts and sugars dissolve. Increase heat, and bring to a boil; cook, stirring constantly, about 3 minutes or until slightly thickened. Stir in rum. Cool slightly.