Nanohana With Mustard Dressing
[Vegan]

For the Nanohana:

1. Cut the greens crosswise into 1 1/2-inch (4 cm) pieces. Set up a large bowl of ice and water. Bring a medium pot of water to a boil over high heat with the salt and drop in the greens. Boil until the stems are just softened, 2–3 minutes, depending on thickness. Scoop out with a wire-mesh sieve and plunge immediately into the ice bath. Once cold to the touch, pull out of the ice water, shake off, and pat dry in a clean tea towel.
2. Drop the greens into a bowl and toss with the dashi to distribute well. Toss with 2 teaspoons of the usukuchi shoyu and set aside.
3. Heat a medium frying pan or grill pan over high heat and, once hot, sear both sides of the usuage until light brown spots appear, 1–2 minutes per side. Halve lengthwise, then cut crosswise into 1/4-inch (5 mm) strips.
4. Drain the greens in a wire-mesh sieve and discard the soaking liquid. Squeeze by handfuls and drop into a medium bowl.
5. In a small bowl, slowly mix the remaining 2 teaspoons usukuchi shoyu, the shoyu, and mustard powder into a paste. Scrape into the bowl of greens and toss well to distribute evenly. Fold in the usuage and serve immediately, mounded into four small bowls.

For the Happo Dashi:

1. In a medium saucepan, stir the konbu dashi, sake, mirin, and salt together. Bring to a simmer over medium heat, reduce to a low simmer, and cook for 2 minutes to burn off the alcohol. Best the first day but still good for 1 or 2 days after, if refrigerated, covered, in a clean jar.