What is added to the basic mixture to make an Irish coffee?

Irish coffee may not be the first coffee drink with alcohol, but this cocktail has become one of the most famous. Combining coffee with Irish whiskey, brown sugar, and lightly whipped cream, the Irish coffee is a hot, creamy classic that can wake you up on cold mornings or keep you going after a long night. There are many stories about Irish Coffee’s origins. The most credible version attributes the cocktail to Joe Sheridan, the head chef of a restaurant in County Limerick, Ireland, in the early 1940s, who wanted to add a little local hospitality to the establishment’s coffee.

Source: Liquor.com