Cook your rice (instructions below).
In a large skillet over medium heat, add 1 tablespoon oil, veggies, and ¼ teaspoon salt. Cook until veggies have softened, about 3-5 minutes, stirring occasionally. Transfer to a bowl.
Meanwhile, in a small bowl, use a fork to mix/mash together the miso, water, ginger, vinegar, soy sauce, and red pepper flakes (if using) until smooth. Set aside.
In the same skillet, add in the remaining 1 tablespoon oil, chicken, and remaining ¼ teaspoon salt. Break it up into chunks and spread out into an even layer and let cook for 5 minutes, stirring halfway through, or until cooked through.
Return the veggies to the skillet along with the miso mixture and stir to coat. Remove from heat.
To make the slaw (if using), add celery to the same bowl that had the veggies in it and toss with vinegar and salt.
Serve topped with fresh herbs and celery slaw (if using). If not using slaw, top with a squeeze of lime and some chopped toasted nuts.