In a microwave-safe bowl, combine the soy sauce, peanut butter, and honey; microwave 1 minute until the peanut butter softens, then whisk until smooth.
Whisk in the coconut milk, grated ginger, and minced garlic to the peanut sauce.
Place the trimmed chicken breasts in the slow cooker and pour the peanut sauce over the chicken.
Cook on low for 4 hours.
After 4 hours, remove 2 teaspoons of the sauce into a small bowl and whisk in 1 teaspoon cornstarch until smooth; stir this back into the slow cooker and continue cooking 45–60 minutes to thicken the sauce.
While the sauce thickens, bring 2 cups water to a boil in a saucepan, add the quinoa, reduce heat to low, cover, and simmer about 15 minutes until water is absorbed.
Stir together the Greek yogurt and 1 tablespoon sriracha in a small bowl; set aside.
In a large bowl, toss the chopped Napa cabbage with 1/2 cup chopped cilantro and the sriracha yogurt; season with a pinch of salt.
Remove the chicken from the slow cooker and shred with two forks, then return it to the sauce and stir to coat.
Divide the cooked quinoa and cabbage slaw among four bowls. Top each bowl with shredded chicken, toasted peanuts, extra cilantro, and extra sriracha if desired. Drizzle any remaining peanut sauce over the bowls and serve.