In a container big enough to fit the chicken, mix together all ingredients for the marinade. Add chicken breasts and let marinate in the fridge for 1 hour.
Medium dice mango and avocado. Transfer to a medium mixing bowl and toss with the rest of the ingredients for the salsa. Taste and adjust seasoning if needed. Let stand in the fridge to allow the flavors to mingle while you prepare the chicken.
After chicken is done marinating, heat up 1 tsp olive oil in a large nonstick skillet over low heat.
Sear chicken breasts on low heat for 10 minutes on each side or until the internal temperature reaches 165°F / 75°C on an instant-read thermometer.
Serve chicken with mango salsa. Enjoy!