A smaller version of espressoA small coffee beverage, about 20 ml, prepared on an espresso machine where pressurized hot water extracted through compressed coffee.: In its most stripped-down, basic form, this is... ...more where extractionRefers to the process of infusing coffee with hot water. Hot water releases or "extracts" the flavor from the roasted, ground coffee. The term is used mostly with... ...more is restricted is called a Ristretto. While espresso averages 20 ml, a ristretto is 15 ml.