In a large bowl combine the napa cabbage, purple cabbage, yellow and red bell pepper.
In a medium skillet, saute the mushrooms in the oil until golden brown, about 8-10 minutes. Once golden, remove and add to the cabbage mixture along with the shredded chicken breasts.
Combine the ingredients for the Ginger Scallion sauce in a bowl. Put half of the sauce aside to use for drizzling, and combine the remaining half with the cabbage and chicken mixture and toss to combine.
Prep the toppings, sliced cucumber, steamed white rice tossed with 1-2 tablespoons of rice wine vinegar, sliced avocados and romaine lettuce.
Arrange the 4 bowl and fill equally with piles of the rice, cucumber, sliced avocado, shredded romaine and the chicken mixture. Drizzle with remaining sauce. Serve as needed.