Add the beef tendon to a pot with plenty of water and boil for 5 minutes.
Rinse thoroughly under running water to remove the scum.
Tear the konjac into bite-sized pieces using a spoon.
Add the beef tendon, 500 ml water, the green part of the Japanese long onion, and sliced ginger to a pot.
Bring to a boil, cover, and simmer over low heat for 1 hour.
Remove the green onion and ginger.
Add the konjac and seasoning mixture A.
Simmer uncovered over medium-low heat for 30 minutes.
Top with chopped green onion and shichimi togarashi if you like.
