I made this dish from the two portions of chiai 血合い (one from the toro block and the other from top loin block) which was marinated over night. This dish may be rather challenging for most Westerners and even for some Japanese. Again,I have posted this before. You could add more soy sauce and put it over rice. We just had this as a drinking snack.
Once the chiai was prepared, the rest was rather easy. I used one small individual package of nattou 納豆 (frozen, made from organic soy beans from Hokkaido,-of course). After thawing the nattou, I mixed in fine chopped scallion, seasoning (tare) and the mustard that came with the nattou and mixed rather vigorously for a few minutes using my favorite nattou mixing contraption. I then separated one egg (As before I used a safe pasteurized egg for this). I added the cubes of marinated chiai and the egg yolk and mixed well. I just garnished it with the finely chopped green part of the scallion.
The gamey strong taste of chiai was a good match for nattou and the egg yolk binds all flavors. I admit this may be the acquired taste.
To clean the palate, I then served tuna sashimi as seen below. This time, I had very fatty tuna (ootro) from the previous night as well as medium fatty tuna (chutoro) and red meat (akami) from the top loin block I prepared this evening. As a garnish, especially since it is the year of the snake, I made snake belly cut mini cucumber or "jabara" 蛇腹 which was soaked in salted water and then seasoned with sushi vinegar (or I could used sweet vinegar). I served it with a tomato rose.
The quality of tuna was very good. Nothing really beats good blue fin tuna.