How is espresso primarily brewed?

Espresso is primarily brewed by forcing hot water through finely ground coffee under high pressure. This method extracts flavors, oils, and aromatic compounds quickly, resulting in a concentrated shot of coffee. The brewing process relies on a pressure of around nine bars, which is crucial for creating the signature crema—a golden foamy layer that sits atop a well-pulled espresso shot. This unique method of brewing distinguishes espresso from other techniques, leading to its rich flavor profile and intense aroma.

The other methods mentioned, while applicable to different brewing techniques, do not accurately describe how espresso is made. For instance, steeping in boiling water is characteristic of brewing methods like French press, which is much less intense than espresso. Soaking beans in cold water refers to cold brewing, which involves a long extraction time and results in a very different coffee flavor. Brewing with air pressure is not a standard method for making espresso, as it lacks the required water pressure essential for the espresso extraction process. Thus, the correct answer highlights the unique and essential technique that defines espresso brewing.