What is the function of a cocktail strainer?

A cocktail strainer serves the essential function of separating liquid from solid ingredients during the cocktail-making process. When a cocktail is prepared, particularly those that involve muddling fruits, herbs, or other solid components, it's necessary to ensure a smooth pour without the solid elements being included in the final drink.

Using a strainer allows bartenders to achieve this by filtering out ice, fruit pulp, or any other solids that may not be desirable in the final presentation of the drink. This results in a clearer and more polished cocktail, enhancing both the visual appeal and the drinking experience.

The other functions described in the choices don't accurately represent the primary role of a cocktail strainer, as mixing ingredients thoroughly involves techniques like shaking or stirring, chilling drinks typically requires ice or refrigeration methods, and aeration is more associated with methods like shaking cocktails to incorporate air. Therefore, separating liquid from solid ingredients is the primary and essential purpose of the cocktail strainer.