What is the primary ingredient used in a Muddled Old Fashioned?

The primary ingredient in a Muddled Old Fashioned is American Whiskey. This classic cocktail traditionally highlights the character and flavor of whiskey, which is often bourbon or rye, but American whiskey encompasses a broad category that fits this classic recipe. The Old Fashioned is known for its simplicity, allowing the whiskey to take center stage, complemented by muddled sugar, bitters, and a twist of citrus.

Muddling in this context refers to the process of mixing the sugar and bitters with a little bit of the whiskey to help dissolve the sugar and incorporate the flavors. The whiskey not only contributes to the drink's backbone but also provides the warmth and complexity that distinguishes an Old Fashioned from other cocktails.

Given the other choices, soda water, champagne, and vodka represent different kinds of cocktails but do not feature the essential characteristics of a Muddled Old Fashioned, which is fundamentally based on the whiskey itself.