Correct Brew Time.
These are elements that must all come together to produce a cup that will mesmerize your tastebuds. If any of these aspects is off you will end up with something amiss in your cup.
Lately, I have been experimenting with vacuum (siphon) coffee brewing and concentrating on the perfection of this brewing method. What looks like a crazy experiment put on by "Mr. Wizard" is one of the best methods for brewing coffee.
After the water approaches boiling in the bottom chamber it begins to create water vapor, which having nowhere else to go, seeks to expand within the confined space and pushes the liquid into the top chamber. The liquid cools slightly while in the top chamber and the continual expansion and condensation of the gas in the lower chamber creates a slightly fluctuating pressure which results in a turbulence in the top chamber. This turbulence, although it looks like boiling water, is not, and I suspect it is one of the primary reasons you can use a short steep/brew time, yet still extract amazing flavors in the cup.
A good butane burner with an adjustable flame will allow you to precisely control the brewing temperature, so rather than a declining temperature, you can maintain a flat line temperature--much like that done in the Synesso Cyncra and Lamarzocco GB5 espresso machines. The theory being that a flat line temperature can more easily extract consistent flavors every time and the ability to adjust the temperature by raising or lowering the flame allows to you find the 'sweet spot' for your particular coffee at hand.
The siphon brewer does its best highlighting the complex, flavorful and bright coffees, and it tends to bring transparency to the deeper flavors. It's like cupping on steroids because once you understand your brew temperature you are given the gift of a multi-dimensional cup that sings with complexity, yet displays an undeniable clarity in each progressive sip.
I will be seeking out several siphon shops in Japan during our visit this December, such as Hanafusa, the first siphon shop in Kyoto.
But until then, I will continue to conjour up some magical brews.