The below picture is an example of a small sashimi dish prepared using a tuna block from Catalina Offshore products. I already mentioned that they did not have blue fine tuna top loin for sometime and belly loin for a longer period. Finally, just in time for New Year, we could get belly loin. Nothing new here but just toro and aburi 炙り or seared toro. Only new item is small cubes of pure tuna fat dressed in sumiso 酢味噌 (in the center back in a small plate).
Before showing where this pure fat came from, here is how the 1 lb of blue fin tuna belly loin looks (#1). This cut has much more chiai or dark red portion as compared top loin. I divided the block into ootoro 大トロ (fattiest), chuutoro 中トロ (meidum fatty), akami 赤身 (red) and chiai 血合い (dark red) (#2 clock wise from the left back). The removed skin (#3) had a thin layer of pure fat. I removed the fat layer with a thin-bladed knife. I pondered what to do with it and came up with this dish; I cut up the fat into small cubes and dressed the pieces with sumiso dressing and chopped scallion.
Fattiest part (#4) often has thin layers of fat separating the meat. I used a kitchen torch and seared them (#5). We also got California gold uni which comes in a wooden pallet as seen here (#6).
You could make your own version of soy sauce for sashimi by adding sake and bonio flakes and heating it up (then strain and cool to room temperature), I just buy a small bottle of commercial “Sashimi Shoyu” 刺身醤油 (left). Since I could not get a fresh wasabi diakon 山葵大根 in time, I thawed real wasabi (right) in a tube, which has its own problem but is the next best.