
Preheat a heatproof glass with hot water and discard the water from the glass.
Shake the cream in a cocktail shaker (or whisk with a small whisk) to a thicker but still fluid consistency.
Add remaining ingredients to the warm glass (sugar, whiskey, then coffee). Ensure the sugar is dissolved and stirred into the coffee and whiskey.
Gently layer heavy cream over the surface of the drink using a flat-bottomed spoon.
Garnish with grated nutmeg and serve at once.