Brewing the perfect shot of espresso is no less a work of art. It involves numerous stages of preparation and precaution. Learning this art requires time and patience, and obviously the willingness to learn. So just in case you have all those, and want to make good espresso with an average semi automatic machine, read on.
First things first. Choose your beans wisely. Buy coffee beans from trusted sources. That way you have more chances to get fresh coffee beans. Once you have your beans in place, let us go into the process of grinding them. An average semi automatic machine will not come with an in built grinder. Hence even before you buy a semi automatic machine, first invest in a good grinder. Also, see to it that you use the coffee as soon as grinding is done. Do not grind your beans very fine. Let them be as course as table salt, and not powdery.
Now that your beans are done, measure the ground coffee out into the portafilter. How much coffee you need to put depends on how strong you want the brew to be and also on the type of coffee beans. This bit, you need to experiment a bit and fix. One standard serving size of espresso requires around 18-20 grams of coffee. Tamping the coffee into the portafilter is important. Tamping is the process by which you can make the ground coffee layer in the portafilter compact. What happens is if the bed of ground coffee is not tamped properly, there are gaps in it. When the water passes through coffee, the gaps make it easier for the water to pass. This leads to poor quality extraction. If the coffee is tamped properly then the water needs to put more effort in passing through it and hence the brewed espresso is much stronger in flavor. There are tampers available in the market. They make tamping way easier than doing it with hands. Get one of those.
The temperature at which the espresso is brewed also decides the fate of the coffee. The ideal temperature is around 92C to 96C. But sadly, most semi automatic home machines fail to maintain a steady temperature and hence there is fluctuation. To get this fixed, you can either add a temperature controller to your machine or you can buy a PID-Controlled espresso machine. To make sure that you will choose the right type of PID-Controlled espresso machine, read espresso machine reviews here.
The extraction time matters. Generally a shot of espresso should not take more or less than thirty seconds. Thirty seconds is good time for optimum espresso extraction.
Additionally flush your group head with hot water once before you attach the portafilter with the coffee to it. If your machine comes with a cup warming tray, then it is all good. Or else you might just want to manually warm you cup a bit by washing it with hot water.
All the steps I described above, are equally important and if you go a little loose on one, you will see a distinct difference in the taste of your brew, immediately.
Apart from all these, and perhaps the most important step in making the perfect espresso is cleaning your espresso making machine regularly. Otherwise the coffee oil from the ground coffee settles down into the portafilter. And this in turn makes the resulting extracted espresso taste weird and rancid. I would suggest cleaning after every brew.
Like I mentioned before, making the perfect cup of espresso takes practice and patience. Repeated practice will help you get your measurements and timings correct. And if you are too lazy to do all this, yet want perfect coffee, please buy a super automatic machine where everything will be done and all you have to do is just press the button. Sounds lucrative? I know. Just that they are a little expensive.
Here is a nice video to demonstrate the whole process. Happy Coffee-ing!