Step 1

Roll the butter with a rolling pin until it is flattened. Add the brown sugar, cinnamon, nutmeg and allspice. Use a spatula the butter together with the sugar and spices until everything is incorporated. Use immediately or refrigerate until making the drinks.

Step 2

Add 1 1/2 tablespoons of the spiced butter to each glass. Add rum and boiling water and stir until combined. If you like a sweeter drink, top with whipped cream.