In a medium-sized bowl, combine the brown sugar, butter and spices until light and fluffy.
Portion 2 tablespoons of the spice butter into each cocktail glass.
Measure 1 1/2 oz of rum into each glass and top with 3/4 cup boiling water.
Stir well to break down the butter.
Add a splash of orange juice and a sprinkling of orange zest.
If you'll be entertaining, you can make the spiced butter mixture ahead of time and refrigerate it for up to one week. However, the mixture does not need to be refrigerated before making cocktails if you plan to serve these right away. Serve these cocktails hot.
You can substitute any dark liquor for the rum. Many people enjoy whiskey or scotch in its place.