In what drink would you find Irish Whiskey as an ingredient?

Irish Coffee is a classic cocktail that specifically includes Irish whiskey as a primary ingredient. This drink combines hot coffee, sugar, and Irish whiskey, topped with a layer of cream. The use of Irish whiskey not only defines the drink but also adds a distinctive flavor profile that complements the coffee and cream, creating a warm, comforting beverage typically enjoyed as an after-dinner drink.

In contrast, the other beverages listed do not feature Irish whiskey. Mexican Coffee generally uses tequila or rum instead, Calypso Coffee might include rums or flavored liqueurs, and Millionaire's Coffee could feature a variety of spirits, but none of them specifically call for Irish whiskey. Therefore, Irish Coffee stands out as the only choice that incorporates this particular whiskey, making it the correct answer.