Coffee drinks are enjoyed all over the world and vary in ingredients, taste, and brewing methods. But espresso is generally expressed the same way across the globe. It all starts with quality roasted coffee beans.
Step one begins with the perfect grind. Because the espresso machine uses pressure to infuse water in and then through the coffee, it is imperative that the grind be very fine. However, there is such a thing as too fine for espresso. If the coffee is over ground, the portafilter will fill up with water and no liquid will be expelled through to the cup.
Once ground correctly, the coffee is tamped down into the portafilter, usually with a hand tamping device. This is where the amount of espresso to be used is determined and some highly trained baristas will even weigh the grounds to a precise amount. The purpose of this is to level out the fine coffee grounds and pack them together so that air does not circulate during the pouring process. Using the right-sized tamper to fit perfectly into your portafilter is highly recommended.
After tamping the coffee, the portafilter is attached to the espresso machine. Generally, this will be a left to right motion stopping once the handle is tight to the machine. If this step is not done correctly, there will be a loss of pressure and thus a leak in the pour. Some portafilters dispense the espresso on both sides, requiring the barista to use either a wide-mouthed cup or two shot glasses.
If you are using a manual machine, you will have more flexibility in how you pour shots. Whereas an automatic machine will likely do many of these steps for you. Check the pressure on your machine and press the brew button until the desired shots are completed. There should be a small amount of crema at the top of the shot glasses of espresso. This is the carbon dioxide extruding from the pressed coffee.