What characterizes the Muddled Old Fashioned cocktail preparation?

The Muddled Old Fashioned cocktail preparation is characterized primarily by muddling fruits and sugar. This method involves crushing typically used ingredients, such as sugar cubes or simple syrup combined with fresh fruit (often an orange slice or maraschino cherry), to release their flavors and aromas before adding the base spirit. This process not only enhances the drink's taste but also provides a visually appealing element with muddled pieces of fruit often visible in the glass.

The other methods mentioned—blending with ice, shaking with vermouth, and stirring with syrup—do not accurately describe the traditional preparation of an Old Fashioned. The Old Fashioned emphasizes the spirit's flavor and the nuances of the muddled fruits and sugar by keeping the drink relatively simple and straightforward, without the dilution and secondary flavors that might come from shaking or blending.