Hot buttered rum is made from a prepared batter, which can be kept in the refrigerator or freezer. To serve, some batter is put into a mug of very hot water and a jigger of good dark rum.
There are many recipes for the batter. Here's one from Pam McKay that uses vanilla ice cream.
Printer-FriendlyHot Buttered Rum
½ q vanilla ice cream, softened
½ lb dark brown sugar
1 c granulated sugar
½ lb butter
water
dark rum
grated nutmeg
Melt butter. Add to blender with sugar and blend well.
Add half of the softened ice cream and belend until sugar is fully
incorporated and mixture is creamy. Add remaining ice cream and blend.
Store batter in refrigerator or freezer.
To serve, boil water. In an Irish coffee mug, add 2 T of batter and a
jigger of rum. Fill with hot water and stir. Dust with grated nutmeg.