Hot buttered rum and ginger toddy

Method

1. Put all the ingredients, apart from the butter and rosemary, in a small pan over a medium heat. Warm, stirring, until the sugar dissolves and the toddy is steaming (don’t boil).
2. Add the butter and stir until melted. Divide the toddy among heatproof glasses or cups, then add a rosemary sprig to each one.