Top-ranked recipe named "Lone Mountain Ranch Hot Buttered Rum"
make a batter of the above ingredients, I sometimes use the blender because it comes out much smoother, but it doesn't really matter as it gets melted. For each serving fill a cup partway with boiling water, add one jigger of rum and two heaping teaspoons of batter. Adjust to taste.
Also good is part rum and part orange liquer.