Fill large (beer or water) glass with ice. Pour all ingredients except the nutmeg into glass. Stir with long spoon until ingredients are mixed. Grate whole nutmeg on top of drink or sprinkle with ground nutmeg.
If you have a bar mixing tin or martini shaker do steps 1 and 2 in the mixing tin/martini shaker, shake and pour into large glass.
Courtesy of Soggy Dollar Bar, British Virgin Islands