The art and science of a good shot of espresso could fill volumes, so we’ll only delve into a few basic principles and in no particular order.
Espresso is not a coffee roast per se, but there are certainly roasts that make a better, bolder shot. The best espresso comes from a blend of Arabica beans that balance dark roasted flavours with sweeter, milder roasts.
More than any other brewing method, espresso demands a very fine, consistent grind some say is close to a powder. Those small hand grinders will not do when making the perfect espresso, you’ll need an adjustable Burr grinder.
Keep your machinery clean. That grinder, the steaming nozzle, et al.
The correct “dose” of espresso grinds for a single shot is 6-8 grams per cup. Double for a double shot, naturally.
Tamp or pack the grinds into a puck with moderate, consistent pressure. Turn the tamper to “polish” the puck.
Extraction time is between 20 and 25 seconds for either single or double shots. Be consistent.
Finished espresso is thick and creamy, with a foamy, orange-brown crema on top.