Excerpted from Cocktail Codex

Irish Coffee

In this Flip variation, the cream isn't mixed into the cocktail; instead, it's whipped and floated on top. Because the heat of the underlying ingredients unravels the structure of the whipped cream, causing it to seep into the liquid in a less-than-appealing way, we recommend whipping the cream until it develops soft peaks so it will hold up longer.

2 ounces heavy cream
1½ ounces Jameson Irish whiskey
¾ ounce Demerara Syrup (see below)
3 ounces hot brewed coffee

Using a bowl and a whisk, whip the cream until soft peaks begin to form. Warm a coffee or toddy mug by filling it with boiling water, letting it sit for a minute or two, then dumping out the water. Pour in the whiskey and syrup, then slowly add the coffee while stirring continuously. Carefully spoon all the whipped cream on top of the drink. 

Demerara Syrup: Combine 2 parts demerara sugar and 1 part water in a sauce pan and cook over medium heat, stirring constantly, until the sugar has dissolved. Transfer to a storage container and refrigerate until ready to use, up to 2 months.