For the base place butter, Maine Maple Syrup, brown sugar, cinnamon and nutmeg in the bowl of a free stand mixer fitted with a paddle attachment, or use a hand mixer. Mix on medium speed for 1-2 minutes.
Place 2 tablespoons of the butter mixture and 2 ounces of rum in each mug. Add 1/4 cup hot water and stir with a spoon. Top with a small scoop of ice cream if desired.