What you'll need:
- 18 grams of specialty-grade whole bean coffee (note: your portafilter basket is rated for some maximum dosage - you want as much coffee as you can fit in the basket without touching the shower screen of your espresso machine; the coffee puck swells as it gets wet)
- Filtered water
- Espresso machine
- Burr grinder
Before we begin, it is necessary to point out that it is very expensive to make good espresso at home. If you haven't spent at least $300 on a grinder, and about the same on the espresso machine itself, it's going to be quite difficult for you to get a good and consistent shot.
1. Preheat machine and portafilter. Purge group head with hot water for a few seconds.
2. Grind the coffee quite fine, but probably not as fine as your grinder will go (unless you have a pretty cheap grinder).
3. Evenly distribute the coffee in the portafilter basket by tapping a bit on each side with your hand.
4. Tamp the grounds down evenly. Tremendous pressure is not necessary.
5. Insert portafilter into group, place your cup on a scale under the group, and start shot. If your machine offers pre-infusion, pre-infuse until some droplets actually start falling into your cup, then turn the pump on.
6. Stop the shot when the scale reads a few grams shy of your desired yield (liquid will keep dripping into the cup for a second or so). If you're using an 18g dose, we recommend starting at a 45g yield (1 to 2.5 ratio). The appropriate amount of time for your shot to reach this yield depends heavily on your grinder and your water. It may range anywhere from 18-45 seconds. Use your taste buds as a guide.
7. If the espresso tastes sour and watery, grind finer. If it tastes sour and strong, increase yield. If it tastes strong and bitter, grind coarser. If it tastes weak and bitter, reduce yield. Don't adjust your dose unless the grounds are contacting the basket (decrease dose), or you can't grind fine enough to get enough extraction (increase dose...and therefore yield as well to keep your ratio the same).