Jajamen said to have originated from a similar Northern Chinese dish known as "Ja Jian Mien" (炸醬麵), and also heavily influenced by the Korean version of Jajangmyeon probably coming from the same root. The recipe made its way to Morioka during or after the war, and now it's modified and served in its own unique way in this part of Japan.
The core ingredients in every Jajamen are pretty much the same - the thick udon noodles, dark miso paste, cucumber and green onion. But each Jajamen shop was said to have its own secret formula of miso paste and own different set of condiments.
When? March 27 2015
Where? Pairon Honten, 5-15 Uchimaru, Morioka, Iwate Prefecture
Tabelog Site: http://tabelog.com/iwate/A0301/A030101/3000037/
(Part of the Japan Rail Trip 2015 Series - a journey through the Tohoku region by rail in spring)