– 1 cup lower-sodium soy sauce – 1/4 cup light brown sugar – 1/4 cup mirin – 1 tablespoon grated fresh ginger (from one 5-inch piece) – 2 teaspoons grated garlic (from 4 medium cloves) – 1 1/2 pounds boneless, skinless chicken thigh
– 2 (7.1-ounce) packages instant udon noodle – 4 medium scallion – 3 tablespoons grapeseed oil, divided – 6 cups low-sodium chicken broth – 3 bunches baby bok choy, separated into individual leave – 1 cup sliced baby bella or crimini mushroom
Combine the soy sauce, sugar, mirin, ginger, and garlic in a large bowl. Add the chicken and toss to coat. Cover securely with plastic wrap and refrigerate for at least 20 minutes, but up to an hour.
Prepare the noodles according to package directions.
Chop the scallions, separating the white and pale green parts from the dark green parts; set aside.
Remove the chicken from the fridge. Place a colander or big strainer over a dish and allow the excess to drop out. Reserve 1/4 cup of the marinade and discard the remainder. In a large nonstick skillet, heat 2 tablespoons oil over medium heat. Cook for 4 to 5 minutes each side, or until the chicken is golden brown on both sides and a thermometer put into it reads 165°F. Move to a medium-sized bowl.
In a large Dutch oven, heat the remaining 1 tablespoon of oil on medium-high. Cook for about a minute, stirring periodically, until the scallions are aromatic and transparent. Add 1/4 cup of the marinade to the Dutch oven. Cook for approximately 2 minutes, stirring regularly, until the sauce thickens. Gradually add the broth, stirring frequently, until well mixed. Bring to a boil on high.
While the broth is heating up, use two forks to shred the chicken into bite-sized pieces. Add the shredded chicken and any collected liquids to the Dutch oven and return to a simmer over medium heat.
Place the bok choy and mushrooms in the Dutch oven and cover. Cook, covered, until the bok choy stalks and mushrooms are soft, about 3 to 5 minutes.
Stir the cooked noodles into the Dutch oven until well combined. Divide the soup into four dishes, garnish with dark green scallions, and serve.