The moka pot is how coffee is prepared in many Italian homes, they use "la moka" which is a 3 piece metal contraption. The bottom part holds the water, the middle part is a funnel shaped filter holding the ground coffee, and the top part receives the coffee. The top part screws tightly (air tight actually) onto the bottom part holding the filter in between. When properly filled and assembled, the moka is put on the stove, the water boils, pressure increases in the bottom part, pushing the water through the coffee into the top reservoir. As the last of the water makes its way with vapor in the top part, it makes a rumbling noise which warns you that coffee is ready. A moka pot makes very good strong coffee.
To brew coffee using a moka pot you will follow the following steps:
1 . Place water in the bottom section of the pot to the level of the valve.
2. Fill the filter basket with ground coffee. Do not tamp it. As the water reaches the grounds they will expand effectively tamping your coffee for you.
3. Put the unit together and place on a medium heat. Brewing should take approximately 5 minutes. If it takes longer use a slightly higher heat.
A warning is in order. Many of the moka pots that are available in the United States are if cheap aluminum construction. Aluminum may leave a distinct bad flavor in your coffee as the coffee reacts with the aluminum. My best advice is to spend the extra money and get a good food grade stainless steel pot if you are going to use a moka pot. As has been commented some people may not notice the aluminum taste so this may not be an issue for everyone. Even for people who notice the flavor a protective layer will eventually form that will block most if not all aluminum flavor. I still prefer steel but will say that aluminum is probably an option.
Even though moka pots are often called stove top espresso machines the coffee they produce is not what is typically thought of as espresso. The entire process is different since while it is steam pressure that pushes the water up to the top chamber very little pressure is involved in the moka. A moka pot has a release valve to assure that excessive pressure does not build up. If you ever happen to see a moka pot without a pressure release valve run away.