1. Combine first 4 ingredients (through rice vinegar) in a small bowl, stirring with a whisk.
2. Heat a large skillet over medium-high heat. Add oil to pan; swirl to coat. Add garlic and ginger to pan; sauté 30 seconds. Add soy sauce mixture and coleslaw; cook 1 minute, stirring frequently. Add chicken and 1/4 cup onions to pan; cook 1 minute or until coleslaw just begins to wilt. Divide chicken mixture evenly among lettuce leaves; sprinkle evenly with remaining 1/4 cup onions and cashews.