In a large sauce pan, melt butter over medium heat.Stir in brown sugar and powdered sugar and stir until well blended. It will be thick and smooth.Remove from heat and stir in the ice cream and spices.Go head and taste it. It's yummy! You may want more nutmeg or cinnamon, feel free to add more.Pour into a freezer safe container and freeze until you're ready for a little drinky poo.This keeps for a little over a month.TO SERVEAdd 1 heaping tablespoon (or more) of the batter to your mug.Add one shot glass of rumFill to the top with boiling water or steaming milk and stir.Top with whipped cream and garnish with a cinnamon stick or a sprinkle of nutmeg.