In a small bowl, combine raisins and rum and let sit 15 minutes.
Meanwhile, in a medium saucepan, combine sugar with 1/4 cup water. Boil over high heat (don't stir) until a spot starts to turn brown, about 8 minutes. Gently swirl pan until sugar is an even amber color.
Carefully whisk cream into sugar mixture (it will boil furiously).
Remove from heat and stir in raisins and rum.
Let cool completely before packaging.
Make ahead: Cool, then cover and chill up to 2 weeks. Reheat to serve.
