Fill coffee mug 3⁄4 full with hot water. Stir in batter until dissolved. Add rum and serve with a stir stick.
To make batter mix, use 1 lb. brown sugar, 1⁄2 lb. salted butter (softened), 2 teaspoons ground cinnamon, 2 teaspoons ground nutmeg, 1⁄2 teaspoon ground allspice, pinch of ground clove, and 1 teaspoon vanilla extract. In a mixing bowl, blend all ingredients together with a hand mixer. Store at room temperature. For a buttered pumpkin batter, simply add pumpkin pie puree to taste (about 1 small can) to batter mix and blend thoroughly.