Add sauce ingredients into a high speed blender or food processor and blend until smooth. (You may have to scrap sides once or twice).
Add chicken, red onion, and red bell pepper into slow cooker. Pour sauce over chicken and veggies.
Cook on low 6-8 hours or high 3-4 hours.
Remove chicken from slow cooker, shred or chop chicken, and mix chicken back into sauce in slow cooker.
Serve over rice and enjoy! Optional: Garnish with fresh parsley and fresh mango if desired.