We had a variation of this dish at Yuzuki in San Francisco and also learned that the original dish was supposedly invented by a small “Teppanyaki” 鉄板焼き place in Hiroshima 広島 called “Naka-chan” 中ちゃん. I decided to try this dish since I got “Premium” uni from Catalina for the weekend: they did not have “Gold” uni (it is getting nearly impossible to get gold uni). The “premium” uni could be OK but this batch was very soft and disintegrating when we received it. The first day, I selected the most well-shaped ones for sashimi which tasted OK but the remaining uni did not fare that well. I thought about making pasta with uni sauce. I then remembered this dish and decided to make it. Initially, I was going to make the one similar to we had at Yuzuki but, after looking at the original dish, which is served with baguette and I happened to have baked baguette in the morning, I made this dish as it is served at Naka-chan (we have never gone there or had the dish in this variation but I based this dish on the description and pictures).
As you can see, we initially served only two thin slices (toasted) baguette rounds so that we would not fill up on this opening dish of the evening.
But we needed more baguette to mop up the wonderful sauce.
Since there is no "recipe", I just “winged it”. In the picture, the original dish appears to use whole water cress with thick stalks attached but I removed thick stalks (the amount is arbitrary, I could have used more watercress). I added about 1tbs of unsalted butter in a frying pan on medium heat. When butter bubbled and started browning, I added the watercress and sautéed until it wilted. Then I added a whole tray of premium uni (120grams) (Picture above). I added about 1 tsp of soy sauce and a squeeze of lemon juice and cut the fire.
This was sublime! It tasted wonderful on top of toasted baguette. We actually had to go get some more baguette because we were not going to leave a single drop of the wonderful sauce behind. The only alteration I would make is to cut up the watercress—the whole watercress became rather stringy. Next time, I may use the thicker stalks but I will chop up the water cress into much smaller pieces. We had this with cold sake but it may also go well with sparkling wine or a crisp acidic white.