2 ounces skim milk, cold
2 1/2 ounces dark rum
1 pinch ground cinnamon
1 pinch of ground cardamom
1 whole egg
Nutmeg, for garnish
Froth the milk well as if for cappuccino.
Shake the remaining ingredients in an ice-filled cocktail shaker and strain into a glass mug.
Top with the frothed milk and garnish with freshly grated nutmeg.