These two servings are made from a half of the tuna block but it turned out to be quite a lot (for us, at least).
Making this is rather simple. This time, modifications included using Vidalia onion (in stead of scallion) and Jalapeno pepper. I cut the tuna into small cubes, added finely chopped, deseeded, and deveined Jalapeno pepper (half of large one), finely chopped Vidalia onion (half of medium sized) and miso (I added a bit more later after I tasted it). In addition, I added the Spanish olive oil we really like. As I "hit" or "tataku" 叩くit with my heavy chef's knife, I gradually added the olive oil to incorporate (instead of using mayonnaise when making negitoro) until it became the pasty consistency and still some small chunks are remaining. I also add a little bit more olive oil on the top as I served this.
Although we started the evening with a Napa cab, we switched to cold sake (We happened to have "Dassai" 獺祭 daiginjo 大吟醸 from Yamaguchi 山口県 prefecture). We thought the addition of Jalapeno to this dish was a good one. It added a fresh pepper taste without adding any heat (since I removed the veins and seeds). Although quite subtle, the addition of olive oil also added to the unctuous texture. The amount of miso was just right and we could really taste nice miso flavors with nutty-saltiness. I had a few more dishes planned but at this point, we were quite full.