Layer ingredients in slow cooker (this classic Crock-pot has lasted us years!) in this order: quinoa, onions, peppers, bok choy, chicken.
In a medium mixing bowl, whisk together liquid ingredients EXCEPT for 2 TB Mirin. Pour this sauce over ingredients in slow cooker. Cover and cook on high for 2 hours.
In a small frying pan over medium heat, quickly saute cashews with 2 TB Mirin for about 20 seconds. The Mirin should caramelize on the cashews, forming a stick-sweet coating like candy. Set aside.
Before serving, top your quinoa chicken with candied cashews, sesame seeds, and sliced green onion.