Tuna sashimi with natto マグロ納豆

We got a 2 lb of block of fresh tuna, sashimi grade, from Catalina Offshore Products (2 lb is the minimum you can order for sashimi-grade fresh tuna). It has ootoro 大トロ, chutoro 中トロ, and a portion called 'chiai" 血合い. You have to first remove the skin and chiai, and then, block out these portions to rectangular blocks called 'saku" 冊 from which sashimi pieces can be cut. In other words, you have to know how to separate these portions to prepare the tuna block from Catalina. After I make the sashimi blocks, I wrap it using kitchen parchment paper, then using a paper towel. I put them in a Ziploc bag and put them back in the Styrofoam container in which the tuna came, add more ice gel packages, which I keep in the freezer, on the top. I put the entire Styrofoam box in our spare refrigerator. This appears to be the best way to keep these sashimi and the ice gels will not totally melt for 5 days or more. I can safely keep them up to 3 days. You could get frozen toro instead, which is easier to prepare since only toro is included, although you have to thaw it. We also tried the frozen toro and the quality is very good.

Chiai is at the edge of chutoro and looks very dark red. If you taste it as sashimi, it has an unpleasant bitter taste. Rather than throwing away this portion, it can be made it to a dish you can enjoy. I decided to make, maguro-natto using natto 納豆; one of the dreaded among Japanese food items.

I cut the chiai portion into small (1/2 to 1/3 inch) cubes and marinated in soy sauce, sake, and mirin mixture (2:1:1). You could add grated ginger (which I did not). I got enough chiai from the 2 lb block for two servings (probably about 100 grams or a bit less than 1/4 lb). I marinate over night in the refrigerator.

Next day just before serving, I prepare a small package (individual serving) of natto as I described before with a sauce and mustard included in the package and using my special mixing apparatus. Add thinly sliced scallion (1/3 to 1/2 scallion) and keep mixing (the longer you mix, the less the odor).

I place the cubes of marinated (excess liquid drained and pat dry) chiai in the bottom of a small bowl, top them with natto and garnish with thin strips of nori. It is rather strong flavored but it is good. This is not a high class food but it is perfect for Izakaya. You have to have this with sake.  Again, even my wife enjoyed this dish. Of course you could make this dish using a regular akami 赤身 (red) tuna or, for that matter, any parts of tuna. I would not marinate or marinate for a shorter time if you use better quality portions of tuna.