Important Tamper & Puck revision January 2013
(new!) Packing the coffee is another of the critical steps to obtain consistently good espresso. I only recently learned this (2005) after a second trip to Italy. Use a tamper or similar circular based tool that just fits the coffee basket diameter. I use a 225 cc vitamin C container. By pressing down with moderate pressure for a man and slightly heavy for a woman you will see the coffee pack down about .25 inches or more from the top of the basket lip. Twist as you press to smooth out the packing of the grounds.
The density of the coffee puck determines the richness of the espresso and, to some extent, its bitterness. It is therefor one of the main elements that you must master to make strong, clean tasting espresso. It can also get a bit complicated and here's what I understand about it now late in my life of making espresso:
COFFEE PUCK-ground granular fineness and packing pressure from using a tamper have a big effect on how easy it is for heated water to flow through the coffee-puck. To allow the coffee-puck to control the espresso you have to leave enough room above it (approx 2-3mm) to allow it to expand without hitting the filter plate above it, otherwise the expansion and filter plate determine coffee puck compaction.
So do some experiments with coffee compacting pressures for a specific grind granularity(different for each coffee bean and grind fineness) to determine which pressure is the maximum you can apply and still have the pressure relief valve not let pressure out because the puck is too dense. Generally this is the puck density you wish to achieve for maximum richness and espresso density without bitterness. Bitterness can also increase as a result of the roast of coffee and heating too fast forcing the hot water up too abruptly.
THE HEAT: Put milk in a sauce pan (I use half half&half and half 2%) and heat at medium till skimmed-over. Heat espresso at same time at high heat till it starts flowing, visible with lid up, then turn to medium. or lower and let flow smoothly into upper chamber until the lovely golden cream foam comes out at the end of the cycle. Turn heat off because the water is gone from lower chamber and damage to the gasket can occur if left on.
THE CUP AND THE POUR: Preheat cup in microwave. Use half teaspoon of sugar in cup first then add espresso to about 1/3 to 1/2 cup height, toss milk in blender, blend on high (watch lid doesn't fly off) (use glass blender, plastic cracks after a while) and tap blender, milk and all, on counter to release large bubbles. Pour with sloshing motion to get foam out. ( Instead of heating on the stove I now heat in the microwave for about a minute. Black and Deckar make a cheap little espresso maker from which i use only the little foamer, a glass beaker and french press like thing that when pumped foams the mild.)
I use two types of cup. For delicate
drinking thin china coffee cups do not cool the coffee down and
feel delicate in the hand. I also like the thick brown half circle
cups used in Florence before 1990. By the way: Italy has lost
the skill they used to have at making every cup perfectly. They
diverted their attention when Starbucks got so pupular. They do
use sugar in Florence!
THE MIX OF MILK AND ESPRESSO: This should not contain much foam. Americans use too much foam. Only a 1/4" layer on top. The rest is 1/3 to 1/2 espresso, and 2/3-1/2 milk.
Stir to mix sugar.
DRINKING: Sit and relax, read, look at the grass, sky, flowers, drink this wonderful brew.