Dissolve 2 teaspoons baking soda in 4 cups of water, and stir to dissolve.
Cut the scallions into 2-inch lengths.
Cut a slit halfway through the scallions lengthwise to their core.
Unfurl the scallion, spreading it out flat. If the scallion has a solid core, remove it and use it for something else.
Slice the scallion into very thin ribbons lengthwise (with the grain). Drop the scallions in the baking soda water and let it tame for at least 15 minutes.
For the seri, use just the leaves and tender stems.
When the scallions are no longer overwhelmingly pungent, drain them and wash them thoroughly with cold water. Spin the scallions and seri in a salad spinner to dry.
Make the dressing by whisking together the soy sauce, rice vinegar, and sugar and set aside.
For the chicken, salt, and pepper both sides to taste.
Put the chicken skin-side down in a non-stick pan and then set a heavy pan on top of the chicken to press it down. Turn the heat on to medium-low and fry until the skin-side is well browned and crisp (7-10 minutes).
Remove the weight and flip the chicken over, frying the second side until the chicken is just cooked through. Transfer the chicken to a cutting board and let it rest.
Toss the scallions and seri with the dressing.
Slice the chicken and plate, topping with the scallion and seri salad.