Pour in the hot coffee. Mix together until the sugar has dissolved.
Add the whiskey and stir again.
Allow the mixture to rest for a few seconds before pouring the cream over the back of a warmed spoon, allowing it to gently settle on top of the coffee.
Serve immediately.
Notes
The cream does not need to be whipped at all, but the added thickness does help it to settle better on top. Partly whipped means it's just starting to thicken, so half of it is lightly whipped but the rest is still runny.